State management cleanup

third_party/WebKit/Source/platform/graphics/gpu/DrawingBuffer.cpp

Index: third_party/WebKit/Source/platform/graphics/gpu/DrawingBuffer.cpp
diff --git a/third_party/WebKit/Source/platform/graphics/gpu/DrawingBuffer.cpp b/third_party/WebKit/Source/platform/graphics/gpu/DrawingBuffer.cpp
index 3f203e79ab4e1599738b39018414a486acfb5f5c..9ba469948d72a2b9a97fab0cd50a2f9c12282000 100644
--- a/third_party/WebKit/Source/platform/graphics/gpu/DrawingBuffer.cpp
+++ b/third_party/WebKit/Source/platform/graphics/gpu/DrawingBuffer.cpp
@@ -60,36 +60,13 @@ namespace {
 
 const float s_resourceAdjustedRatio = 0.5;
 
-class ScopedTextureUnit0BindingRestorer {
-  STACK_ALLOCATED();
-  WTF_MAKE_NONCOPYABLE(ScopedTextureUnit0BindingRestorer);
-
- public:
-  ScopedTextureUnit0BindingRestorer(gpu::gles2::GLES2Interface* gl,
-                                    GLenum activeTextureUnit,
-                                    GLuint textureUnitZeroId)
-      : m_gl(gl),
-        m_oldActiveTextureUnit(activeTextureUnit),
-        m_oldTextureUnitZeroId(textureUnitZeroId) {
-    m_gl->ActiveTexture(GL_TEXTURE0);
-  }
-  ~ScopedTextureUnit0BindingRestorer() {
-    m_gl->BindTexture(GL_TEXTURE_2D, m_oldTextureUnitZeroId);
-    m_gl->ActiveTexture(m_oldActiveTextureUnit);
-  }
-
- private:
-  gpu::gles2::GLES2Interface* m_gl;
-  GLenum m_oldActiveTextureUnit;
-  GLuint m_oldTextureUnitZeroId;
-};
-
 static bool shouldFailDrawingBufferCreationForTesting = false;
 
 }  // namespace
 
 PassRefPtr<DrawingBuffer> DrawingBuffer::create(
     std::unique_ptr<WebGraphicsContext3DProvider> contextProvider,
+    DrawingBufferStateTracker* drawingBufferRestoreSource,
     const IntSize& size,
     bool premultipliedAlpha,
     bool wantAlphaChannel,
@@ -137,9 +114,9 @@ PassRefPtr<DrawingBuffer> DrawingBuffer::create(
 
   RefPtr<DrawingBuffer> drawingBuffer = adoptRef(new DrawingBuffer(
       std::move(contextProvider), std::move(extensionsUtil),
-      discardFramebufferSupported, wantAlphaChannel, premultipliedAlpha,
-      preserve, webGLVersion, wantDepthBuffer, wantStencilBuffer,
-      chromiumImageUsage));
+      drawingBufferRestoreSource, discardFramebufferSupported, wantAlphaChannel,
+      premultipliedAlpha, preserve, webGLVersion, wantDepthBuffer,
+      wantStencilBuffer, chromiumImageUsage));
   if (!drawingBuffer->initialize(size, multisampleSupported)) {
     drawingBuffer->beginDestruction();
     return PassRefPtr<DrawingBuffer>();
@@ -154,6 +131,7 @@ void DrawingBuffer::forceNextDrawingBufferCreationToFail() {
 DrawingBuffer::DrawingBuffer(
     std::unique_ptr<WebGraphicsContext3DProvider> contextProvider,
     std::unique_ptr<Extensions3DUtil> extensionsUtil,
+    DrawingBufferStateTracker* stateTracker,
     bool discardFramebufferSupported,
     bool wantAlphaChannel,
     bool premultipliedAlpha,
@@ -162,7 +140,8 @@ DrawingBuffer::DrawingBuffer(
     bool wantDepth,
     bool wantStencil,
     ChromiumImageUsage chromiumImageUsage)
-    : m_preserveDrawingBuffer(preserve),
+    : m_stateTracker(stateTracker),
+      m_preserveDrawingBuffer(preserve),
       m_webGLVersion(webGLVersion),
       m_contextProvider(std::move(contextProvider)),
       m_gl(m_contextProvider->contextGL()),
@@ -174,8 +153,6 @@ DrawingBuffer::DrawingBuffer(
       m_wantDepth(wantDepth),
       m_wantStencil(wantStencil),
       m_chromiumImageUsage(chromiumImageUsage) {
-  memset(m_colorMask, 0, 4 * sizeof(GLboolean));
-  memset(m_clearColor, 0, 4 * sizeof(GLfloat));
   // Used by browser tests to detect the use of a DrawingBuffer.
   TRACE_EVENT_INSTANT0("test_gpu", "DrawingBufferCreation",
                        TRACE_EVENT_SCOPE_GLOBAL);
@@ -217,7 +194,7 @@ void DrawingBuffer::setIsHidden(bool hidden) {
     return;
   m_isHidden = hidden;
   if (m_isHidden)
-    m_recycledMailboxQueue.clear();
+    m_recycledColorBufferQueue.clear();
 }
 
 void DrawingBuffer::setFilterQuality(SkFilterQuality filterQuality) {
@@ -229,7 +206,9 @@ void DrawingBuffer::setFilterQuality(SkFilterQuality filterQuality) {
 }
 
 bool DrawingBuffer::requiresAlphaChannelToBePreserved() {
-  return !m_drawFramebufferBinding &&
+  DrawingBufferRestoreState restoreState;
+  m_stateTracker->GetDrawingBufferRestoreState(&restoreState);
+  return !restoreState.drawFramebufferBinding &&
          defaultBufferRequiresAlphaChannelToBePreserved();
 }
 
@@ -265,6 +244,7 @@ std::unique_ptr<cc::SharedBitmap> DrawingBuffer::createOrRecycleBitmap() {
 bool DrawingBuffer::PrepareTextureMailbox(
     cc::TextureMailbox* outMailbox,
     std::unique_ptr<cc::SingleReleaseCallback>* outReleaseCallback) {
+  ScopedStateRestorer scopedStateRestorer(this);
   bool forceGpuResult = false;
   return prepareTextureMailboxInternal(outMailbox, outReleaseCallback,
                                        forceGpuResult);
@@ -299,107 +279,124 @@ bool DrawingBuffer::prepareTextureMailboxInternal(
 
   // Resolve the multisampled buffer into m_backColorBuffer texture.
   if (m_antiAliasingMode != None)
-    commit();
+    resolveMultisampleFramebufferInternal();
 
   if (m_softwareRendering && !forceGpuResult) {
-    std::unique_ptr<cc::SharedBitmap> bitmap = createOrRecycleBitmap();
-    if (!bitmap)
-      return false;
+    return finishPrepareTextureMailboxSoftware(outMailbox, outReleaseCallback);
+  } else {
+    return finishPrepareTextureMailboxGpu(outMailbox, outReleaseCallback);
+  }
+}
+
+bool DrawingBuffer::finishPrepareTextureMailboxSoftware(
+    cc::TextureMailbox* outMailbox,
+    std::unique_ptr<cc::SingleReleaseCallback>* outReleaseCallback) {
+  std::unique_ptr<cc::SharedBitmap> bitmap = createOrRecycleBitmap();
+  if (!bitmap)
+    return false;
+
+  // Read the framebuffer into |bitmap|.
+  {
     unsigned char* pixels = bitmap->pixels();
     DCHECK(pixels);
-
     bool needPremultiply = m_wantAlphaChannel && !m_premultipliedAlpha;
     WebGLImageConversion::AlphaOp op =
         needPremultiply ? WebGLImageConversion::AlphaDoPremultiply
                         : WebGLImageConversion::AlphaDoNothing;
     readBackFramebuffer(pixels, size().width(), size().height(), ReadbackSkia,
                         op);
+  }
 
-    *outMailbox = cc::TextureMailbox(bitmap.get(), m_size);
+  *outMailbox = cc::TextureMailbox(bitmap.get(), m_size);
 
-    // This holds a ref on the DrawingBuffer that will keep it alive until the
-    // mailbox is released (and while the release callback is running). It also
-    // owns the SharedBitmap.
-    auto func = WTF::bind(&DrawingBuffer::softwareMailboxReleased,
-                          RefPtr<DrawingBuffer>(this),
-                          WTF::passed(std::move(bitmap)), m_size);
-    *outReleaseCallback = cc::SingleReleaseCallback::Create(
-        convertToBaseCallback(std::move(func)));
-    return true;
-  }
+  // This holds a ref on the DrawingBuffer that will keep it alive until the
+  // mailbox is released (and while the release callback is running). It also
+  // owns the SharedBitmap.
+  auto func = WTF::bind(&DrawingBuffer::mailboxReleasedSoftware,
+                        RefPtr<DrawingBuffer>(this),
+                        WTF::passed(std::move(bitmap)), m_size);
+  *outReleaseCallback =
+      cc::SingleReleaseCallback::Create(convertToBaseCallback(std::move(func)));
+  return true;
+}
 
+bool DrawingBuffer::finishPrepareTextureMailboxGpu(
+    cc::TextureMailbox* outMailbox,
+    std::unique_ptr<cc::SingleReleaseCallback>* outReleaseCallback) {
   if (m_webGLVersion > WebGL1) {
+    m_stateRestorer->setPixelUnpackBufferBindingDirty();
     m_gl->BindBuffer(GL_PIXEL_UNPACK_BUFFER, 0);
   }
 
-  // We must restore the texture binding since creating new textures,
-  // consuming and producing mailboxes changes it.
-  ScopedTextureUnit0BindingRestorer restorer(m_gl, m_activeTextureUnit,
-                                             m_texture2DBinding);
-
-  // First try to recycle an old buffer.
-  RefPtr<ColorBuffer> colorBufferForMailbox = takeRecycledMailbox();
-
-  // No buffer available to recycle, create a new one.
-  if (!colorBufferForMailbox)
-    colorBufferForMailbox = createTextureAndAllocateMemory(m_size);
-
+  // Specify the buffer that we will put in the mailbox.
+  RefPtr<ColorBuffer> colorBufferForMailbox;
   if (m_preserveDrawingBuffer == Discard) {
-    std::swap(colorBufferForMailbox, m_backColorBuffer);
+    // If we can discard the backbuffer, send the old backbuffer directly
+    // into the mailbox, and allocate (or recycle) a new backbuffer.
+    colorBufferForMailbox = m_backColorBuffer;
+    m_backColorBuffer = createOrRecycleColorBuffer();
     attachColorBufferToReadFramebuffer();
 
+    // Explicitly specify that m_fbo (which is now bound to the just-allocated
+    // m_backColorBuffer) is not initialized, to save GPU memory bandwidth for
+    // tile-based GPU architectures.
     if (m_discardFramebufferSupported) {
-      // Explicitly discard the framebuffer to save GPU memory bandwidth for
-      // tile-based GPU arch.
       const GLenum attachments[3] = {GL_COLOR_ATTACHMENT0, GL_DEPTH_ATTACHMENT,
                                      GL_STENCIL_ATTACHMENT};
+      m_stateRestorer->setFramebufferBindingDirty();
       m_gl->BindFramebuffer(GL_FRAMEBUFFER, m_fbo);
       m_gl->DiscardFramebufferEXT(GL_FRAMEBUFFER, 3, attachments);
     }
   } else {
+    // If we can't discard the backbuffer, create (or recycle) a buffer to put
+    // in the mailbox, and copy backbuffer's contents there.
+    colorBufferForMailbox = createOrRecycleColorBuffer();
     m_gl->CopySubTextureCHROMIUM(
         m_backColorBuffer->textureId, colorBufferForMailbox->textureId, 0, 0, 0,
         0, m_size.width(), m_size.height(), GL_FALSE, GL_FALSE, GL_FALSE);
   }
 
-  restoreFramebufferBindings();
-  restorePixelUnpackBufferBindings();
-  m_contentsChanged = false;
-
-  m_gl->ProduceTextureDirectCHROMIUM(colorBufferForMailbox->textureId,
-                                     colorBufferForMailbox->parameters.target,
-                                     colorBufferForMailbox->mailbox.name);
-  const GLuint64 fenceSync = m_gl->InsertFenceSyncCHROMIUM();
+  // Put colorBufferForMailbox into its mailbox, and populate its
+  // produceSyncToken with that point.
+  {
+    m_gl->ProduceTextureDirectCHROMIUM(colorBufferForMailbox->textureId,
+                                       colorBufferForMailbox->parameters.target,
+                                       colorBufferForMailbox->mailbox.name);
+    const GLuint64 fenceSync = m_gl->InsertFenceSyncCHROMIUM();
 #if OS(MACOSX)
-  m_gl->DescheduleUntilFinishedCHROMIUM();
+    m_gl->DescheduleUntilFinishedCHROMIUM();
 #endif
-  m_gl->Flush();
-  gpu::SyncToken syncToken;
-  m_gl->GenSyncTokenCHROMIUM(fenceSync, syncToken.GetData());
+    m_gl->Flush();
+    m_gl->GenSyncTokenCHROMIUM(
+        fenceSync, colorBufferForMailbox->produceSyncToken.GetData());
+  }
 
-  bool isOverlayCandidate = colorBufferForMailbox->imageId != 0;
-  bool secureOutputOnly = false;
-  *outMailbox = cc::TextureMailbox(colorBufferForMailbox->mailbox, syncToken,
-                                   colorBufferForMailbox->parameters.target,
-                                   gfx::Size(m_size.width(), m_size.height()),
-                                   isOverlayCandidate, secureOutputOnly);
+  // Populate the output mailbox and callback.
+  {
+    bool isOverlayCandidate = colorBufferForMailbox->imageId != 0;
+    bool secureOutputOnly = false;
+    *outMailbox = cc::TextureMailbox(
+        colorBufferForMailbox->mailbox, colorBufferForMailbox->produceSyncToken,
+        colorBufferForMailbox->parameters.target, gfx::Size(m_size),
+        isOverlayCandidate, secureOutputOnly);
 
-  // This holds a ref on the DrawingBuffer that will keep it alive until the
-  // mailbox is released (and while the release callback is running).
-  auto func = WTF::bind(&DrawingBuffer::gpuMailboxReleased,
-                        RefPtr<DrawingBuffer>(this), colorBufferForMailbox);
-  *outReleaseCallback =
-      cc::SingleReleaseCallback::Create(convertToBaseCallback(std::move(func)));
+    // This holds a ref on the DrawingBuffer that will keep it alive until the
+    // mailbox is released (and while the release callback is running).
+    auto func = WTF::bind(&DrawingBuffer::mailboxReleasedGpu,
+                          RefPtr<DrawingBuffer>(this), colorBufferForMailbox);
+    *outReleaseCallback = cc::SingleReleaseCallback::Create(
+        convertToBaseCallback(std::move(func)));
+  }
 
-  // Point |m_frontColorBuffer| to the buffer that we are presenting, and
-  // update its sync token.
-  colorBufferForMailbox->produceSyncToken = syncToken;
+  // Point |m_frontColorBuffer| to the buffer that we are now presenting.
   m_frontColorBuffer = colorBufferForMailbox;
+
+  m_contentsChanged = false;
   setBufferClearNeeded(true);
   return true;
 }
 
-void DrawingBuffer::gpuMailboxReleased(RefPtr<ColorBuffer> colorBuffer,
+void DrawingBuffer::mailboxReleasedGpu(RefPtr<ColorBuffer> colorBuffer,
                                        const gpu::SyncToken& syncToken,
                                        bool lostResource) {
   // If the mailbox has been returned by the compositor then it is no
@@ -422,13 +419,13 @@ void DrawingBuffer::gpuMailboxReleased(RefPtr<ColorBuffer> colorBuffer,
   size_t cacheLimit = 1;
   if (shouldUseChromiumImage())
     cacheLimit = 4;
-  while (m_recycledMailboxQueue.size() >= cacheLimit)
-    m_recycledMailboxQueue.takeLast();
+  while (m_recycledColorBufferQueue.size() >= cacheLimit)
+    m_recycledColorBufferQueue.takeLast();
 
-  m_recycledMailboxQueue.prepend(colorBuffer);
+  m_recycledColorBufferQueue.prepend(colorBuffer);
 }
 
-void DrawingBuffer::softwareMailboxReleased(
+void DrawingBuffer::mailboxReleasedSoftware(
     std::unique_ptr<cc::SharedBitmap> bitmap,
     const IntSize& size,
     const gpu::SyncToken& syncToken,
@@ -442,6 +439,8 @@ void DrawingBuffer::softwareMailboxReleased(
 }
 
 PassRefPtr<StaticBitmapImage> DrawingBuffer::transferToStaticBitmapImage() {
+  ScopedStateRestorer scopedStateRestorer(this);
+
   // This can be null if the context is lost before the first call to
   // grContext().
   GrContext* grContext = m_contextProvider->grContext();
@@ -514,12 +513,12 @@ PassRefPtr<StaticBitmapImage> DrawingBuffer::transferToStaticBitmapImage() {
       std::move(skImage), skImageMailbox, skImageSyncToken);
 }
 
-DrawingBuffer::TextureParameters
-DrawingBuffer::chromiumImageTextureParameters() {
+DrawingBuffer::ColorBufferParameters
+DrawingBuffer::gpuMemoryBufferColorBufferParameters() {
 #if OS(MACOSX)
   // A CHROMIUM_image backed texture requires a specialized set of parameters
   // on OSX.
-  TextureParameters parameters;
+  ColorBufferParameters parameters;
   parameters.target = GC3D_TEXTURE_RECTANGLE_ARB;
 
   if (m_wantAlphaChannel) {
@@ -541,12 +540,13 @@ DrawingBuffer::chromiumImageTextureParameters() {
   parameters.colorFormat = 0;
   return parameters;
 #else
-  return defaultTextureParameters();
+  return textureColorBufferParameters();
 #endif
 }
 
-DrawingBuffer::TextureParameters DrawingBuffer::defaultTextureParameters() {
-  TextureParameters parameters;
+DrawingBuffer::ColorBufferParameters
+DrawingBuffer::textureColorBufferParameters() {
+  ColorBufferParameters parameters;
   parameters.target = GL_TEXTURE_2D;
   if (m_wantAlphaChannel) {
     parameters.internalColorFormat = GL_RGBA;
@@ -568,37 +568,65 @@ DrawingBuffer::TextureParameters DrawingBuffer::defaultTextureParameters() {
   return parameters;
 }
 
-PassRefPtr<DrawingBuffer::ColorBuffer> DrawingBuffer::takeRecycledMailbox() {
-  if (m_recycledMailboxQueue.isEmpty())
-    return nullptr;
-
-  RefPtr<ColorBuffer> recycled = m_recycledMailboxQueue.takeLast();
-  DCHECK(recycled->size == m_size);
-  if (recycled->receiveSyncToken.HasData())
-    m_gl->WaitSyncTokenCHROMIUM(recycled->receiveSyncToken.GetData());
-  return recycled;
+PassRefPtr<DrawingBuffer::ColorBuffer>
+DrawingBuffer::createOrRecycleColorBuffer() {
+  if (!m_recycledColorBufferQueue.isEmpty()) {
+    RefPtr<ColorBuffer> recycled = m_recycledColorBufferQueue.takeLast();
+    if (recycled->receiveSyncToken.HasData())
+      m_gl->WaitSyncTokenCHROMIUM(recycled->receiveSyncToken.GetData());
+    DCHECK(recycled->size == m_size);
+    return recycled;
+  }
+  return createColorBuffer(m_size);
 }
 
 DrawingBuffer::ColorBuffer::ColorBuffer(DrawingBuffer* drawingBuffer,
-                                        const TextureParameters& parameters,
-                                        const IntSize& size)
-    : drawingBuffer(drawingBuffer), parameters(parameters), size(size) {
+                                        const ColorBufferParameters& parameters,
+                                        const IntSize& size,
+                                        GLuint textureId,
+                                        GLuint imageId)
+    : drawingBuffer(drawingBuffer),
+      parameters(parameters),
+      size(size),
+      textureId(textureId),
+      imageId(imageId) {
   drawingBuffer->contextGL()->GenMailboxCHROMIUM(mailbox.name);
 }
 
 DrawingBuffer::ColorBuffer::~ColorBuffer() {
-  gpu::gles2::GLES2Interface* gl = drawingBuffer->contextGL();
+  gpu::gles2::GLES2Interface* gl = drawingBuffer->m_gl;
   if (receiveSyncToken.HasData())
     gl->WaitSyncTokenCHROMIUM(receiveSyncToken.GetConstData());
   if (imageId) {
     gl->BindTexture(parameters.target, textureId);
     gl->ReleaseTexImage2DCHROMIUM(parameters.target, imageId);
     gl->DestroyImageCHROMIUM(imageId);
+    switch (parameters.target) {
+      case GL_TEXTURE_2D:
+        // Restore the texture binding for GL_TEXTURE_2D, since the client will
+        // expect the previous state.
+        if (drawingBuffer->m_stateTracker) {
+          DrawingBufferRestoreState restoreState;
+          drawingBuffer->m_stateTracker->GetDrawingBufferRestoreState(
+              &restoreState);
+          gl->BindTexture(GL_TEXTURE_2D, restoreState.activeTexture2DBinding);
+        }
+        break;
+      case GC3D_TEXTURE_RECTANGLE_ARB:
+        // Rectangle textures aren't exposed to WebGL, so don't bother
+        // restoring this state (there is no meaningful way to restore it).
+        break;
+      default:
+        NOTREACHED();
+        break;
+    }
   }
   gl->DeleteTextures(1, &textureId);
 }
 
 bool DrawingBuffer::initialize(const IntSize& size, bool useMultisampling) {
+  ScopedStateRestorer scopedStateRestorer(this);
+
   if (m_gl->GetGraphicsResetStatusKHR() != GL_NO_ERROR) {
     // Need to try to restore the context again later.
     return false;
@@ -630,6 +658,7 @@ bool DrawingBuffer::initialize(const IntSize& size, bool useMultisampling) {
       m_antiAliasingMode == ScreenSpaceAntialiasing;
   m_sampleCount = std::min(4, maxSampleCount);
 
+  m_stateRestorer->setFramebufferBindingDirty();
   m_gl->GenFramebuffers(1, &m_fbo);
   m_gl->BindFramebuffer(GL_FRAMEBUFFER, m_fbo);
   if (wantExplicitResolve()) {
@@ -637,7 +666,7 @@ bool DrawingBuffer::initialize(const IntSize& size, bool useMultisampling) {
     m_gl->BindFramebuffer(GL_FRAMEBUFFER, m_multisampleFBO);
     m_gl->GenRenderbuffers(1, &m_multisampleRenderbuffer);
   }
-  if (!reset(size))
+  if (!resizeFramebufferInternal(size))
     return false;
 
   if (m_depthStencilBuffer) {
@@ -662,11 +691,11 @@ bool DrawingBuffer::copyToPlatformTexture(gpu::gles2::GLES2Interface* gl,
                                           bool premultiplyAlpha,
                                           bool flipY,
                                           SourceDrawingBuffer sourceBuffer) {
+  ScopedStateRestorer scopedStateRestorer(this);
+
   if (m_contentsChanged) {
-    if (m_antiAliasingMode != None) {
-      commit();
-      restoreFramebufferBindings();
-    }
+    if (m_antiAliasingMode != None)
+      resolveMultisampleFramebufferInternal();
     m_gl->Flush();
   }
 
@@ -722,10 +751,6 @@ bool DrawingBuffer::copyToPlatformTexture(gpu::gles2::GLES2Interface* gl,
   return true;
 }
 
-GLuint DrawingBuffer::framebuffer() const {
-  return m_fbo;
-}
-
 WebLayer* DrawingBuffer::platformLayer() {
   if (!m_layer) {
     m_layer = wrapUnique(
@@ -754,7 +779,7 @@ void DrawingBuffer::beginDestruction() {
   m_destructionInProgress = true;
 
   clearPlatformLayer();
-  m_recycledMailboxQueue.clear();
+  m_recycledColorBufferQueue.clear();
 
   if (m_multisampleFBO)
     m_gl->DeleteFramebuffers(1, &m_multisampleFBO);
@@ -779,26 +804,19 @@ void DrawingBuffer::beginDestruction() {
 
   if (m_layer)
     GraphicsLayer::unregisterContentsLayer(m_layer->layer());
-}
 
-GLuint DrawingBuffer::createColorTexture(const TextureParameters& parameters) {
-  GLuint offscreenColorTexture;
-  m_gl->GenTextures(1, &offscreenColorTexture);
-  m_gl->BindTexture(parameters.target, offscreenColorTexture);
-  m_gl->TexParameteri(parameters.target, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
-  m_gl->TexParameteri(parameters.target, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
-  m_gl->TexParameteri(parameters.target, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
-  m_gl->TexParameteri(parameters.target, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
-  return offscreenColorTexture;
+  m_stateTracker = nullptr;
 }
 
 bool DrawingBuffer::resizeDefaultFramebuffer(const IntSize& size) {
   // Recreate m_backColorBuffer.
-  m_backColorBuffer = createTextureAndAllocateMemory(size);
+  m_backColorBuffer = createColorBuffer(size);
 
   attachColorBufferToReadFramebuffer();
 
   if (wantExplicitResolve()) {
+    m_stateRestorer->setFramebufferBindingDirty();
+    m_stateRestorer->setRenderbufferBindingDirty();
     m_gl->BindFramebuffer(GL_FRAMEBUFFER, m_multisampleFBO);
     m_gl->BindRenderbuffer(GL_RENDERBUFFER, m_multisampleRenderbuffer);
     m_gl->RenderbufferStorageMultisampleCHROMIUM(
@@ -813,6 +831,8 @@ bool DrawingBuffer::resizeDefaultFramebuffer(const IntSize& size) {
   }
 
   if (wantDepthOrStencil()) {
+    m_stateRestorer->setFramebufferBindingDirty();
+    m_stateRestorer->setRenderbufferBindingDirty();
     m_gl->BindFramebuffer(GL_FRAMEBUFFER,
                           m_multisampleFBO ? m_multisampleFBO : m_fbo);
     if (!m_depthStencilBuffer)
@@ -839,17 +859,25 @@ bool DrawingBuffer::resizeDefaultFramebuffer(const IntSize& size) {
   }
 
   if (wantExplicitResolve()) {
+    m_stateRestorer->setFramebufferBindingDirty();
     m_gl->BindFramebuffer(GL_FRAMEBUFFER, m_multisampleFBO);
     if (m_gl->CheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE)
       return false;
   }
 
+  m_stateRestorer->setFramebufferBindingDirty();
   m_gl->BindFramebuffer(GL_FRAMEBUFFER, m_fbo);
   return m_gl->CheckFramebufferStatus(GL_FRAMEBUFFER) ==
          GL_FRAMEBUFFER_COMPLETE;
 }
 
 void DrawingBuffer::clearFramebuffers(GLbitfield clearMask) {
+  ScopedStateRestorer scopedStateRestorer(this);
+  clearFramebuffersInternal(clearMask);
+}
+
+void DrawingBuffer::clearFramebuffersInternal(GLbitfield clearMask) {
+  m_stateRestorer->setFramebufferBindingDirty();
   // We will clear the multisample FBO, but we also need to clear the
   // non-multisampled buffer.
   if (m_multisampleFBO) {
@@ -878,7 +906,12 @@ IntSize DrawingBuffer::adjustSize(const IntSize& desiredSize,
   return adjustedSize;
 }
 
-bool DrawingBuffer::reset(const IntSize& newSize) {
+bool DrawingBuffer::resize(const IntSize& newSize) {
+  ScopedStateRestorer scopedStateRestorer(this);
+  return resizeFramebufferInternal(newSize);
+}
+
+bool DrawingBuffer::resizeFramebufferInternal(const IntSize& newSize) {
   CHECK(!newSize.isEmpty());
   IntSize adjustedSize = adjustSize(newSize, m_size, m_maxTextureSize);
   if (adjustedSize.isEmpty())
@@ -896,13 +929,14 @@ bool DrawingBuffer::reset(const IntSize& newSize) {
     m_size = adjustedSize;
     // Free all mailboxes, because they are now of the wrong size. Only the
     // first call in this loop has any effect.
-    m_recycledMailboxQueue.clear();
+    m_recycledColorBufferQueue.clear();
     m_recycledBitmaps.clear();
 
     if (adjustedSize.isEmpty())
       return false;
   }
 
+  m_stateRestorer->setClearStateDirty();
   m_gl->Disable(GL_SCISSOR_TEST);
   m_gl->ClearColor(0, 0, 0,
                    defaultBufferRequiresAlphaChannelToBePreserved() ? 1 : 0);
@@ -920,17 +954,25 @@ bool DrawingBuffer::reset(const IntSize& newSize) {
     m_gl->StencilMaskSeparate(GL_FRONT, 0xFFFFFFFF);
   }
 
-  clearFramebuffers(clearMask);
+  clearFramebuffersInternal(clearMask);
   return true;
 }
 
-void DrawingBuffer::commit() {
+void DrawingBuffer::resolveAndBindForReadAndDraw() {
+  {
+    ScopedStateRestorer scopedStateRestorer(this);
+    resolveMultisampleFramebufferInternal();
+  }
+  m_gl->BindFramebuffer(GL_FRAMEBUFFER, m_fbo);
+}
+
+void DrawingBuffer::resolveMultisampleFramebufferInternal() {
+  m_stateRestorer->setFramebufferBindingDirty();
   if (wantExplicitResolve() && !m_contentsChangeCommitted) {
+    m_stateRestorer->setClearStateDirty();
     m_gl->BindFramebuffer(GL_READ_FRAMEBUFFER_ANGLE, m_multisampleFBO);
     m_gl->BindFramebuffer(GL_DRAW_FRAMEBUFFER_ANGLE, m_fbo);
-
-    if (m_scissorEnabled)
-      m_gl->Disable(GL_SCISSOR_TEST);
+    m_gl->Disable(GL_SCISSOR_TEST);
 
     int width = m_size.width();
     int height = m_size.height();
@@ -949,52 +991,18 @@ void DrawingBuffer::commit() {
             .disable_multisampling_color_mask_usage) {
       m_gl->ClearColor(0, 0, 0, 1);
       m_gl->ColorMask(false, false, false, true);
-      m_gl->Clear(GL_COLOR_BUFFER_BIT);
-
-      m_gl->ClearColor(m_clearColor[0], m_clearColor[1], m_clearColor[2],
-                       m_clearColor[3]);
-      m_gl->ColorMask(m_colorMask[0], m_colorMask[1], m_colorMask[2],
-                      m_colorMask[3]);
     }
-
-    if (m_scissorEnabled)
-      m_gl->Enable(GL_SCISSOR_TEST);
   }
 
   m_gl->BindFramebuffer(GL_FRAMEBUFFER, m_fbo);
-  if (m_antiAliasingMode == ScreenSpaceAntialiasing) {
+  if (m_antiAliasingMode == ScreenSpaceAntialiasing)
     m_gl->ApplyScreenSpaceAntialiasingCHROMIUM();
-  }
   m_contentsChangeCommitted = true;
 }
 
-void DrawingBuffer::restorePixelUnpackBufferBindings() {
-  if (m_webGLVersion > WebGL1) {
-    m_gl->BindBuffer(GL_PIXEL_UNPACK_BUFFER, m_pixelUnpackBufferBinding);
-  }
-}
-
 void DrawingBuffer::restoreFramebufferBindings() {
-  if (m_drawFramebufferBinding && m_readFramebufferBinding) {
-    if (m_drawFramebufferBinding == m_readFramebufferBinding) {
-      m_gl->BindFramebuffer(GL_FRAMEBUFFER, m_readFramebufferBinding);
-    } else {
-      m_gl->BindFramebuffer(GL_READ_FRAMEBUFFER, m_readFramebufferBinding);
-      m_gl->BindFramebuffer(GL_DRAW_FRAMEBUFFER, m_drawFramebufferBinding);
-    }
-    return;
-  }
-  if (!m_drawFramebufferBinding && !m_readFramebufferBinding) {
-    bind(GL_FRAMEBUFFER);
-    return;
-  }
-  if (!m_drawFramebufferBinding) {
-    bind(GL_DRAW_FRAMEBUFFER);
-    m_gl->BindFramebuffer(GL_READ_FRAMEBUFFER, m_readFramebufferBinding);
-  } else {
-    bind(GL_READ_FRAMEBUFFER);
-    m_gl->BindFramebuffer(GL_DRAW_FRAMEBUFFER, m_drawFramebufferBinding);
-  }
+  DrawingBufferRestoreState restoreState;
+  m_stateRestorer->setFramebufferBindingDirty();
 }
 
 bool DrawingBuffer::multisample() const {
@@ -1006,15 +1014,13 @@ void DrawingBuffer::bind(GLenum target) {
                         wantExplicitResolve() ? m_multisampleFBO : m_fbo);
 }
 
-void DrawingBuffer::setPackAlignment(GLint param) {
-  m_packAlignment = param;
-}
-
 bool DrawingBuffer::paintRenderingResultsToImageData(
     int& width,
     int& height,
     SourceDrawingBuffer sourceBuffer,
     WTF::ArrayBufferContents& contents) {
+  ScopedStateRestorer scopedStateRestorer(this);
+
   ASSERT(!m_premultipliedAlpha);
   width = size().width();
   height = size().height();
@@ -1030,6 +1036,7 @@ bool DrawingBuffer::paintRenderingResultsToImageData(
                                   WTF::ArrayBufferContents::DontInitialize);
 
   GLuint fbo = 0;
+  m_stateRestorer->setFramebufferBindingDirty();
   if (sourceBuffer == FrontBuffer && m_frontColorBuffer) {
     m_gl->GenFramebuffers(1, &fbo);
     m_gl->BindFramebuffer(GL_FRAMEBUFFER, fbo);
@@ -1037,7 +1044,7 @@ bool DrawingBuffer::paintRenderingResultsToImageData(
                                m_frontColorBuffer->parameters.target,
                                m_frontColorBuffer->textureId, 0);
   } else {
-    m_gl->BindFramebuffer(GL_FRAMEBUFFER, framebuffer());
+    m_gl->BindFramebuffer(GL_FRAMEBUFFER, m_fbo);
   }
 
   readBackFramebuffer(static_cast<unsigned char*>(pixels.data()), width, height,
@@ -1050,8 +1057,6 @@ bool DrawingBuffer::paintRenderingResultsToImageData(
     m_gl->DeleteFramebuffers(1, &fbo);
   }
 
-  restoreFramebufferBindings();
-
   pixels.transfer(contents);
   return true;
 }
@@ -1061,11 +1066,9 @@ void DrawingBuffer::readBackFramebuffer(unsigned char* pixels,
                                         int height,
                                         ReadbackOrder readbackOrder,
                                         WebGLImageConversion::AlphaOp op) {
-  if (m_packAlignment > 4)
-    m_gl->PixelStorei(GL_PACK_ALIGNMENT, 1);
+  m_stateRestorer->setPixelPackAlignmentDirty();
+  m_gl->PixelStorei(GL_PACK_ALIGNMENT, 1);
   m_gl->ReadPixels(0, 0, width, height, GL_RGBA, GL_UNSIGNED_BYTE, pixels);
-  if (m_packAlignment > 4)
-    m_gl->PixelStorei(GL_PACK_ALIGNMENT, m_packAlignment);
 
   size_t bufferSize = 4 * width * height;
 
@@ -1093,100 +1096,96 @@ void DrawingBuffer::readBackFramebuffer(unsigned char* pixels,
 void DrawingBuffer::flipVertically(uint8_t* framebuffer,
                                    int width,
                                    int height) {
-  m_scanline.resize(width * 4);
-  uint8_t* scanline = &m_scanline[0];
+  std::vector<uint8_t> scanline(width * 4);
   unsigned rowBytes = width * 4;
   unsigned count = height / 2;
   for (unsigned i = 0; i < count; i++) {
     uint8_t* rowA = framebuffer + i * rowBytes;
     uint8_t* rowB = framebuffer + (height - i - 1) * rowBytes;
-    memcpy(scanline, rowB, rowBytes);
+    memcpy(scanline.data(), rowB, rowBytes);
     memcpy(rowB, rowA, rowBytes);
-    memcpy(rowA, scanline, rowBytes);
+    memcpy(rowA, scanline.data(), rowBytes);
   }
 }
 
-void DrawingBuffer::allocateConditionallyImmutableTexture(GLenum target,
-                                                          GLenum internalformat,
-                                                          GLsizei width,
-                                                          GLsizei height,
-                                                          GLint border,
-                                                          GLenum format,
-                                                          GLenum type) {
-  if (m_storageTextureSupported) {
-    GLenum internalStorageFormat = GL_NONE;
-    if (internalformat == GL_RGB) {
-      internalStorageFormat = GL_RGB8;
-    } else if (internalformat == GL_RGBA) {
-      internalStorageFormat = GL_RGBA8;
-    } else {
-      NOTREACHED();
-    }
-    m_gl->TexStorage2DEXT(GL_TEXTURE_2D, 1, internalStorageFormat, width,
-                          height);
-    return;
+RefPtr<DrawingBuffer::ColorBuffer> DrawingBuffer::createColorBuffer(
+    const IntSize& size) {
+  m_stateRestorer->setFramebufferBindingDirty();
+  m_stateRestorer->setTextureBindingDirty();
+
+  // Select the Parameters for the texture object. Allocate the backing
+  // GpuMemoryBuffer and GLImage, if one is going to be used.
+  ColorBufferParameters parameters;
+  GLuint imageId = 0;
+  if (shouldUseChromiumImage()) {
+    parameters = gpuMemoryBufferColorBufferParameters();
+    imageId = m_gl->CreateGpuMemoryBufferImageCHROMIUM(
+        size.width(), size.height(), parameters.creationInternalColorFormat,
+        GC3D_SCANOUT_CHROMIUM);
+  } else {
+    parameters = textureColorBufferParameters();
   }
-  m_gl->TexImage2D(target, 0, internalformat, width, height, border, format,
-                   type, 0);
-}
-
-void DrawingBuffer::clearChromiumImageAlpha(const ColorBuffer& info) {
-  if (m_wantAlphaChannel)
-    return;
-  if (!contextProvider()->getCapabilities().chromium_image_rgb_emulation)
-    return;
-
-  GLuint fbo = 0;
-  m_gl->GenFramebuffers(1, &fbo);
-  m_gl->BindFramebuffer(GL_FRAMEBUFFER, fbo);
-  m_gl->FramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0,
-                             info.parameters.target, info.textureId, 0);
-  m_gl->ClearColor(0, 0, 0, 1);
-  m_gl->ColorMask(false, false, false, true);
-  m_gl->Clear(GL_COLOR_BUFFER_BIT);
-  m_gl->FramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0,
-                             info.parameters.target, 0, 0);
-  m_gl->DeleteFramebuffers(1, &fbo);
-  restoreFramebufferBindings();
-  m_gl->ClearColor(m_clearColor[0], m_clearColor[1], m_clearColor[2],
-                   m_clearColor[3]);
-  m_gl->ColorMask(m_colorMask[0], m_colorMask[1], m_colorMask[2],
-                  m_colorMask[3]);
-}
 
-RefPtr<DrawingBuffer::ColorBuffer>
-DrawingBuffer::createTextureAndAllocateMemory(const IntSize& size) {
-  if (!shouldUseChromiumImage())
-    return createDefaultTextureAndAllocateMemory(size);
+  // Allocate the texture for this object.
+  GLuint textureId = 0;
+  {
+    m_gl->GenTextures(1, &textureId);
+    m_gl->BindTexture(parameters.target, textureId);
+    m_gl->TexParameteri(parameters.target, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
+    m_gl->TexParameteri(parameters.target, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
+    m_gl->TexParameteri(parameters.target, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
+    m_gl->TexParameteri(parameters.target, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
+  }
 
-  TextureParameters parameters = chromiumImageTextureParameters();
-  GLuint imageId = m_gl->CreateGpuMemoryBufferImageCHROMIUM(
-      size.width(), size.height(), parameters.creationInternalColorFormat,
-      GC3D_SCANOUT_CHROMIUM);
-  GLuint textureId = createColorTexture(parameters);
+  // If this is GpuMemoryBuffer-backed, then bind the texture to the
+  // GpuMemoryBuffer's GLImage. Otherwise, allocate ordinary texture storage.
   if (imageId) {
     m_gl->BindTexImage2DCHROMIUM(parameters.target, imageId);
+  } else {
+    if (m_storageTextureSupported) {
+      GLenum internalStorageFormat = GL_NONE;
+      if (parameters.creationInternalColorFormat == GL_RGB) {
+        internalStorageFormat = GL_RGB8;
+      } else if (parameters.creationInternalColorFormat == GL_RGBA) {
+        internalStorageFormat = GL_RGBA8;
+      } else {
+        NOTREACHED();
+      }
+      m_gl->TexStorage2DEXT(GL_TEXTURE_2D, 1, internalStorageFormat,
+                            size.width(), size.height());
+    } else {
+      m_gl->TexImage2D(parameters.target, 0,
+                       parameters.creationInternalColorFormat, size.width(),
+                       size.height(), 0, parameters.colorFormat,
+                       GL_UNSIGNED_BYTE, 0);
+    }
   }
 
-  RefPtr<ColorBuffer> info(adoptRef(new ColorBuffer(this, parameters, size)));
-  info->textureId = textureId;
-  info->imageId = imageId;
-  clearChromiumImageAlpha(*info);
-  return info;
-}
+  // Clear the alpha channel if this is RGB emulated.
+  if (imageId && !m_wantAlphaChannel &&
+      contextProvider()->getCapabilities().chromium_image_rgb_emulation) {
+    GLuint fbo = 0;
 
-RefPtr<DrawingBuffer::ColorBuffer>
-DrawingBuffer::createDefaultTextureAndAllocateMemory(const IntSize& size) {
-  TextureParameters parameters = defaultTextureParameters();
-  RefPtr<ColorBuffer> info(adoptRef(new ColorBuffer(this, parameters, size)));
-  info->textureId = createColorTexture(parameters);
-  allocateConditionallyImmutableTexture(
-      parameters.target, parameters.creationInternalColorFormat, size.width(),
-      size.height(), 0, parameters.colorFormat, GL_UNSIGNED_BYTE);
-  return info;
+    m_stateRestorer->setClearStateDirty();
+    m_gl->GenFramebuffers(1, &fbo);
+    m_gl->BindFramebuffer(GL_FRAMEBUFFER, fbo);
+    m_gl->FramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0,
+                               parameters.target, textureId, 0);
+    m_gl->ClearColor(0, 0, 0, 1);
+    m_gl->ColorMask(false, false, false, true);
+    m_gl->Clear(GL_COLOR_BUFFER_BIT);
+    m_gl->FramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0,
+                               parameters.target, 0, 0);
+    m_gl->DeleteFramebuffers(1, &fbo);
+  }
+
+  return adoptRef(new ColorBuffer(this, parameters, size, textureId, imageId));
 }
 
 void DrawingBuffer::attachColorBufferToReadFramebuffer() {
+  m_stateRestorer->setFramebufferBindingDirty();
+  m_stateRestorer->setTextureBindingDirty();
+
   m_gl->BindFramebuffer(GL_FRAMEBUFFER, m_fbo);
 
   GLenum target = m_backColorBuffer->parameters.target;
@@ -1200,9 +1199,6 @@ void DrawingBuffer::attachColorBufferToReadFramebuffer() {
   else
     m_gl->FramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, target, id,
                                0);
-
-  restoreTextureBindings();
-  restoreFramebufferBindings();
 }
 
 bool DrawingBuffer::wantExplicitResolve() {
@@ -1227,11 +1223,58 @@ GLenum DrawingBuffer::getMultisampledRenderbufferFormat() {
   return GL_RGB8_OES;
 }
 
-void DrawingBuffer::restoreTextureBindings() {
-  // This class potentially modifies the bindings for GL_TEXTURE_2D and
-  // GL_TEXTURE_RECTANGLE. Only GL_TEXTURE_2D needs to be restored since
-  // the public interface for WebGL does not support GL_TEXTURE_RECTANGLE.
-  m_gl->BindTexture(GL_TEXTURE_2D, m_texture2DBinding);
+DrawingBuffer::ScopedStateRestorer::ScopedStateRestorer(
+    DrawingBuffer* drawingBuffer)
+    : m_drawingBuffer(drawingBuffer) {
+  DCHECK(!m_drawingBuffer->m_stateRestorer);
+  m_drawingBuffer->m_stateRestorer = this;
+}
+
+DrawingBuffer::ScopedStateRestorer::~ScopedStateRestorer() {
+  m_drawingBuffer->m_stateRestorer = nullptr;
+  if (!m_drawingBuffer->m_stateTracker)
+    return;
+
+  gpu::gles2::GLES2Interface* gl = m_drawingBuffer->m_gl;
+  DrawingBufferRestoreState restoreState;
+  m_drawingBuffer->m_stateTracker->GetDrawingBufferRestoreState(&restoreState);
+
+  if (m_clearStateDirty) {
+    if (restoreState.scissorEnabled)
+      gl->Enable(GL_SCISSOR_TEST);
+    else
+      gl->Disable(GL_SCISSOR_TEST);
+    gl->ClearColor(restoreState.clearColor[0], restoreState.clearColor[1],
+                   restoreState.clearColor[2], restoreState.clearColor[3]);
+    gl->ClearDepthf(restoreState.clearDepth);
+    gl->ClearStencil(restoreState.clearStencil);
+
+    gl->ColorMask(restoreState.colorMask[0], restoreState.colorMask[1],
+                  restoreState.colorMask[2], restoreState.colorMask[3]);
+    gl->DepthMask(restoreState.depthMask);
+    gl->StencilMaskSeparate(GL_FRONT, restoreState.stencilMask);
+  }
+  if (m_pixelPackAlignmentDirty)
+    gl->PixelStorei(GL_PACK_ALIGNMENT, restoreState.packAlignment);
+  if (m_textureBindingDirty)
+    gl->BindTexture(GL_TEXTURE_2D, restoreState.activeTexture2DBinding);
+  if (m_renderbufferBindingDirty)
+    gl->BindRenderbuffer(GL_RENDERBUFFER, restoreState.renderbufferBinding);
+  if (m_framebufferBindingDirty) {
+    if (restoreState.drawFramebufferBinding ==
+        restoreState.readFramebufferBinding) {
+      gl->BindFramebuffer(GL_FRAMEBUFFER, restoreState.drawFramebufferBinding);
+    } else {
+      gl->BindFramebuffer(GL_READ_FRAMEBUFFER,
+                          restoreState.readFramebufferBinding);
+      gl->BindFramebuffer(GL_DRAW_FRAMEBUFFER,
+                          restoreState.drawFramebufferBinding);
+    }
+  }
+  if (m_pixelUnpackBufferBindingDirty) {
+    gl->BindBuffer(GL_PIXEL_UNPACK_BUFFER,
+                   restoreState.pixelUnpackBufferBinding);
+  }
 }
 
 bool DrawingBuffer::shouldUseChromiumImage() {