Avoid GPU readback in tex(Sub)Image2D(ImageBitmap)

third_party/WebKit/Source/platform/graphics/StaticBitmapImage.cpp

Index: third_party/WebKit/Source/platform/graphics/StaticBitmapImage.cpp
diff --git a/third_party/WebKit/Source/platform/graphics/StaticBitmapImage.cpp b/third_party/WebKit/Source/platform/graphics/StaticBitmapImage.cpp
index aa45be3a01e44effe6753dd2faabf2521862b325..36262d30efc748ca4d507e89ad355d1b2588fcd4 100644
--- a/third_party/WebKit/Source/platform/graphics/StaticBitmapImage.cpp
+++ b/third_party/WebKit/Source/platform/graphics/StaticBitmapImage.cpp
@@ -14,6 +14,7 @@
 #include "third_party/skia/include/core/SkImage.h"
 #include "third_party/skia/include/core/SkPaint.h"
 #include "third_party/skia/include/core/SkShader.h"
+#include "third_party/skia/include/gpu/GrContext.h"
 #include "wtf/PtrUtil.h"
 #include <memory>
 
@@ -44,9 +45,16 @@ StaticBitmapImage::~StaticBitmapImage() { }
 
 IntSize StaticBitmapImage::size() const
 {
+    if (!m_image)
+        return IntSize(m_mailbox.textureSize.width, m_mailbox.textureSize.height);
     return IntSize(m_image->width(), m_image->height());
 }
 
+bool StaticBitmapImage::isTextureBacked()
+{
+    return m_image && m_image->isTextureBacked();
+}
+
 bool StaticBitmapImage::currentFrameKnownToBeOpaque(MetadataMode)
 {
     return m_image->isOpaque();
@@ -68,23 +76,16 @@ void StaticBitmapImage::draw(SkCanvas* canvas, const SkPaint& paint, const Float
         observer->didDraw(this);
 }
 
-PassRefPtr<SkImage> StaticBitmapImage::imageForCurrentFrame()
+GLuint StaticBitmapImage::switchStorageToSkImage(WebGraphicsContext3DProvider* provider)
 {
-    if (m_image)
-        return m_image;
-    DCHECK(isMainThread());
-    // In the place when we consume an ImageBitmap that is gpu texture backed,
-    // create a new SkImage from that texture.
-    // TODO(xidachen): make this work on a worker thread.
-    std::unique_ptr<WebGraphicsContext3DProvider> provider = wrapUnique(Platform::current()->createSharedOffscreenGraphicsContext3DProvider());
     if (!provider)
-        return nullptr;
+        return 0;
     GrContext* grContext = provider->grContext();
     if (!grContext)
-        return nullptr;
+        return 0;
     gpu::gles2::GLES2Interface* gl = provider->contextGL();
     if (!gl)
-        return nullptr;
+        return 0;
     gl->WaitSyncTokenCHROMIUM(m_mailbox.syncToken);
     GLuint textureId = gl->CreateAndConsumeTextureCHROMIUM(GL_TEXTURE_2D, m_mailbox.name);
     GrGLTextureInfo textureInfo;
@@ -98,6 +99,83 @@ PassRefPtr<SkImage> StaticBitmapImage::imageForCurrentFrame()
     backendTexture.fTextureHandle = skia::GrGLTextureInfoToGrBackendObject(textureInfo);
     sk_sp<SkImage> skImage = SkImage::MakeFromAdoptedTexture(grContext, backendTexture);
     m_image = fromSkSp(skImage);
+    return textureId;
+}
+
+void StaticBitmapImage::copyToTexture(WebGraphicsContext3DProvider* provider, GLuint textureId, GLuint destinationTexture, GLenum internalFormat, GLenum destType, bool flipY)
+{
+    gpu::gles2::GLES2Interface* gl = provider->contextGL();
+    if (!gl)
+        return;
+    gl->CopyTextureCHROMIUM(textureId, destinationTexture, internalFormat, destType, flipY, false, false);
+    const GLuint64 fenceSync = gl->InsertFenceSyncCHROMIUM();
+    gl->Flush();
+    GLbyte syncToken[24];
+    gl->GenSyncTokenCHROMIUM(fenceSync, syncToken);
+}
+
+bool StaticBitmapImage::switchStorageToMailbox(WebGraphicsContext3DProvider* provider)
+{
+    m_mailbox.textureSize = WebSize(m_image->width(), m_image->height());
+    GrContext* grContext = provider->grContext();
+    if (!grContext)
+        return false;
+    grContext->flush();
+    m_mailbox.textureTarget = GL_TEXTURE_2D;
+    gpu::gles2::GLES2Interface* gl = provider->contextGL();
+    if (!gl)
+        return false;
+    GLuint textureID = skia::GrBackendObjectToGrGLTextureInfo(m_image->getTextureHandle(true))->fID;
+    gl->BindTexture(GL_TEXTURE_2D, textureID);
+
+    gl->GenMailboxCHROMIUM(m_mailbox.name);
+    gl->ProduceTextureCHROMIUM(GL_TEXTURE_2D, m_mailbox.name);
+    const GLuint64 fenceSync = gl->InsertFenceSyncCHROMIUM();
+    gl->Flush();
+    gl->GenSyncTokenCHROMIUM(fenceSync, m_mailbox.syncToken);
+    m_mailbox.validSyncToken = true;
+    gl->BindTexture(GL_TEXTURE_2D, 0);
+    grContext->resetContext(kTextureBinding_GrGLBackendState);
+    return true;
+}
+
+// This function is called only in the case that m_image is texture backed.
+GLuint StaticBitmapImage::textureIdForWebGL(WebGraphicsContext3DProvider* contextProvider)
+{
+    DCHECK(!m_image || m_image->isTextureBacked());
+    GLuint textureId = 0;
+    if (m_image) {
+        // SkImage is texture-backed on the shared context
+        if (!hasMailbox()) {
+            std::unique_ptr<WebGraphicsContext3DProvider> sharedProvider = wrapUnique(Platform::current()->createSharedOffscreenGraphicsContext3DProvider());
+            if (!switchStorageToMailbox(sharedProvider.get()))
+                return 0;
+            textureId = switchStorageToSkImage(contextProvider);
+            // Get a new mailbox because we cannot retain a texture in the WebGL context.
+            if (!switchStorageToMailbox(contextProvider))
+                return 0;
+            return textureId;
+        }
+    }
+    DCHECK(hasMailbox());
+    textureId = switchStorageToSkImage(contextProvider);
+    if (!switchStorageToMailbox(contextProvider))
+        return 0;
+    return textureId;
+}
+
+PassRefPtr<SkImage> StaticBitmapImage::imageForCurrentFrame()
+{
+    if (m_image)
+        return m_image;
+    // No mailbox, return null;
+    if (!hasMailbox())
+        return nullptr;
+    // Has mailbox, consume mailbox, prepare a new mailbox if contextProvider is not null (3D).
+    DCHECK(isMainThread());
+    // TODO(xidachen): make this work on a worker thread.
+    std::unique_ptr<WebGraphicsContext3DProvider> sharedProvider = wrapUnique(Platform::current()->createSharedOffscreenGraphicsContext3DProvider());
+    switchStorageToSkImage(sharedProvider.get());

[Ken Russell (switch to Gerrit), 2016/06/24 01:25:10]

What happens if switchStorageToSkImage returns 0? Should this still return
m_image?

[xidachen, 2016/06/24 14:36:07]

Change it to return nullptr in that case.

     return m_image;
 }