Implement client side PBOs for glReadPixel

content/common/gpu/client/gl_helper.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/common/gpu/client/gl_helper.h"
 
 #include <queue>
 
 #include "base/bind.h"
+#include "base/debug/trace_event.h"
 #include "base/lazy_instance.h"
 #include "base/logging.h"
-#include "base/memory/ref_counted.h"
 #include "base/message_loop.h"
-#include "base/synchronization/lock.h"
-#include "base/synchronization/waitable_event.h"
-#include "base/threading/thread.h"
-#include "base/threading/thread_restrictions.h"
+#include "base/time.h"
 #include "third_party/WebKit/Source/Platform/chromium/public/WebCString.h"
 #include "third_party/WebKit/Source/Platform/chromium/public/WebString.h"
 #include "third_party/skia/include/core/SkRegion.h"
 #include "ui/gfx/rect.h"
 #include "ui/gfx/size.h"
 #include "ui/gl/gl_bindings.h"
 
 using WebKit::WebGLId;
 using WebKit::WebGraphicsContext3D;
 
 namespace {
 
-const char kGLHelperThreadName[] = "GLHelperThread";
-
-class GLHelperThread : public base::Thread {
- public:
-  GLHelperThread() : base::Thread(kGLHelperThreadName) {
-    Start();
-  }
-  virtual ~GLHelperThread() {
-    Stop();
-  }
-
- private:
-  DISALLOW_COPY_AND_ASSIGN(GLHelperThread);
-};
-
-base::LazyInstance<GLHelperThread> g_gl_helper_thread =
-    LAZY_INSTANCE_INITIALIZER;
-
 class ScopedWebGLId {
  public:
   typedef void (WebGraphicsContext3D::*DeleteFunc)(WebGLId);
   ScopedWebGLId(WebGraphicsContext3D* context,
                 WebGLId id,
                 DeleteFunc delete_func)
       : context_(context),
         id_(id),
         delete_func_(delete_func) {
   }
@@ skipping 34 matching lines @@
 
 class ScopedFramebuffer : public ScopedWebGLId {
  public:
   ScopedFramebuffer(WebGraphicsContext3D* context,
                     WebGLId id)
       : ScopedWebGLId(context,
                       id,
                       &WebGraphicsContext3D::deleteFramebuffer) {}
 };
 
-class ScopedRenderbuffer : public ScopedWebGLId {
- public:
-  ScopedRenderbuffer(WebGraphicsContext3D* context,
-                     WebGLId id)
-      : ScopedWebGLId(context,
-                      id,
-                      &WebGraphicsContext3D::deleteRenderbuffer) {}
-};
-
 class ScopedProgram : public ScopedWebGLId {
  public:
   ScopedProgram(WebGraphicsContext3D* context,
                 WebGLId id)
       : ScopedWebGLId(context,
                       id,
                       &WebGraphicsContext3D::deleteProgram) {}
 };
 
 class ScopedShader : public ScopedWebGLId {
@@ skipping 16 matching lines @@
 
 template <WebKit::WGC3Denum target>
 class ScopedBinder {
  public:
   typedef void (WebGraphicsContext3D::*BindFunc)(WebKit::WGC3Denum,
                                                          WebGLId);
   ScopedBinder(WebGraphicsContext3D* context,
                WebGLId id,
                BindFunc bind_func)
       : context_(context),
-        id_(id),
         bind_func_(bind_func) {
-    (context_->*bind_func_)(target, id_);
+    (context_->*bind_func_)(target, id);
   }
 
   virtual ~ScopedBinder() {
-    if (id_ != 0)
-      (context_->*bind_func_)(target, 0);
+    (context_->*bind_func_)(target, 0);
   }
 
  private:
   WebGraphicsContext3D* context_;
-  WebGLId id_;
   BindFunc bind_func_;
 
   DISALLOW_COPY_AND_ASSIGN(ScopedBinder);
 };
 
 template <WebKit::WGC3Denum target>
 class ScopedBufferBinder : ScopedBinder<target> {
  public:
   ScopedBufferBinder(WebGraphicsContext3D* context,
                      WebGLId id)
       : ScopedBinder<target>(
           context,
           id,
           &WebGraphicsContext3D::bindBuffer) {}
 };
 
 template <WebKit::WGC3Denum target>
 class ScopedFramebufferBinder : ScopedBinder<target> {
  public:
   ScopedFramebufferBinder(WebGraphicsContext3D* context,
                           WebGLId id)
       : ScopedBinder<target>(
           context,
           id,
           &WebGraphicsContext3D::bindFramebuffer) {}
 };
 
 template <WebKit::WGC3Denum target>
-class ScopedRenderbufferBinder : ScopedBinder<target> {
- public:
-  ScopedRenderbufferBinder(WebGraphicsContext3D* context,
-                           WebGLId id)
-      : ScopedBinder<target>(
-          context,
-          id,
-          &WebGraphicsContext3D::bindRenderbuffer) {}
-};
-
-template <WebKit::WGC3Denum target>
 class ScopedTextureBinder : ScopedBinder<target> {
  public:
   ScopedTextureBinder(WebGraphicsContext3D* context,
                       WebGLId id)
       : ScopedBinder<target>(
           context,
           id,
           &WebGraphicsContext3D::bindTexture) {}
 };
 
 class ScopedFlush {
  public:
   explicit ScopedFlush(WebGraphicsContext3D* context)
       : context_(context) {
   }
 
   virtual ~ScopedFlush() {
     context_->flush();
   }
 
  private:
   WebGraphicsContext3D* context_;
 
   DISALLOW_COPY_AND_ASSIGN(ScopedFlush);
 };
 
-void DeleteContext(WebGraphicsContext3D* context) {
-  delete context;
-}
-
-void SignalWaitableEvent(base::WaitableEvent* event) {
-  event->Signal();
-}
-
 }  // namespace
 
 namespace content {
 
 // Implements GLHelper::CropScaleReadbackAndCleanTexture and encapsulates the
 // data needed for it.
-class GLHelper::CopyTextureToImpl {
+class GLHelper::CopyTextureToImpl :
+      public base::SupportsWeakPtr<GLHelper::CopyTextureToImpl> {
  public:
   CopyTextureToImpl(WebGraphicsContext3D* context,
-                    WebGraphicsContext3D* context_for_thread,
                     GLHelper* helper)
       : context_(context),
-        context_for_thread_(context_for_thread),
         helper_(helper),
         flush_(context),
         program_(context, context->createProgram()),
         vertex_attributes_buffer_(context_, context_->createBuffer()),
         flipped_vertex_attributes_buffer_(context_, context_->createBuffer()) {
     InitBuffer();
     InitProgram();
   }
   ~CopyTextureToImpl() {
     CancelRequests();
-    DeleteContextForThread();
   }
 
   void InitBuffer();
   void InitProgram();
 
   void CropScaleReadbackAndCleanTexture(
       WebGLId src_texture,
       const gfx::Size& src_size,
       const gfx::Rect& src_subrect,
       const gfx::Size& dst_size,
       unsigned char* out,
       const base::Callback<void(bool)>& callback);
 
   void ReadbackTextureSync(WebGLId texture,
                            const gfx::Rect& src_rect,
                            unsigned char* out);
 
   WebKit::WebGLId CopyAndScaleTexture(WebGLId texture,
                                       const gfx::Size& src_size,
                                       const gfx::Size& dst_size,
                                       bool vertically_flip_texture);
 
  private:
   // A single request to CropScaleReadbackAndCleanTexture.
-  // Thread-safety notes: the main thread creates instances of this class. The
-  // main thread can cancel the request, before it's handled by the helper
+  // The main thread can cancel the request, before it's handled by the helper
   // thread, by resetting the texture and pixels fields. Alternatively, the
   // thread marks that it handles the request by resetting the pixels field
   // (meaning it guarantees that the callback with be called).
   // In either case, the callback must be called exactly once, and the texture
   // must be deleted by the main thread context.
-  struct Request : public base::RefCountedThreadSafe<Request> {
-    Request(CopyTextureToImpl* impl,
-            WebGLId texture_,
+  struct Request {
+    Request(WebGLId texture_,
             const gfx::Size& size_,
             unsigned char* pixels_,
             const base::Callback<void(bool)>& callback_)
-        : copy_texture_impl(impl),
-        size(size_),
-        callback(callback_),
-        lock(),
-        texture(texture_),
-        pixels(pixels_) {
+        : size(size_),
+          callback(callback_),
+          texture(texture_),
+          pixels(pixels_),
+          buffer(0),
+          query(0) {
     }
 
-    // These members are only accessed on the main thread.
-    GLHelper::CopyTextureToImpl* copy_texture_impl;
     gfx::Size size;
     base::Callback<void(bool)> callback;
 
-    // Locks access to below members, which can be accessed on any thread.
-    base::Lock lock;
     WebGLId texture;
     unsigned char* pixels;
-
-   private:
-    friend class base::RefCountedThreadSafe<Request>;
-    ~Request() {}
+    GLuint buffer;
+    GLuint query;
   };
 
   // Copies the block of pixels specified with |src_subrect| from |src_texture|,
   // scales it to |dst_size|, writes it into a texture, and returns its ID.
   // |src_size| is the size of |src_texture|.
   WebGLId ScaleTexture(WebGLId src_texture,
                        const gfx::Size& src_size,
                        const gfx::Rect& src_subrect,
                        const gfx::Size& dst_size,
                        bool vertically_flip_texture);
 
-  // Deletes the context for GLHelperThread.
-  void DeleteContextForThread();
-  static void ReadBackFramebuffer(scoped_refptr<Request> request,
-                                  WebGraphicsContext3D* context,
-                                  scoped_refptr<base::TaskRunner> reply_loop);
-  static void ReadBackFramebufferComplete(scoped_refptr<Request> request,
-                                          bool result);
-  void FinishRequest(scoped_refptr<Request> request);
+  void ScheduleCheckReadbackDone();
+  void CheckReadbackDone();
+  void FinishRequest(Request* request, bool result);
   void CancelRequests();
 
   // Interleaved array of 2-dimentional vertex positions (x, y) and
   // 2-dimentional texture coordinates (s, t).
   static const WebKit::WGC3Dfloat kVertexAttributes[];
   // Interleaved array of 2-dimensional vertex positions (x, y) and
   // 2 dimensional texture coordinates (s, t).
   static const WebKit::WGC3Dfloat kFlippedVertexAttributes[];
   // Shader sources used for GLHelper::CropScaleReadbackAndCleanTexture and
   // GLHelper::ReadbackTextureSync
   static const WebKit::WGC3Dchar kCopyVertexShader[];
   static const WebKit::WGC3Dchar kCopyFragmentShader[];
 
   WebGraphicsContext3D* context_;
-  WebGraphicsContext3D* context_for_thread_;
   GLHelper* helper_;
 
   // A scoped flush that will ensure all resource deletions are flushed when
   // this object is destroyed. Must be declared before other Scoped* fields.
   ScopedFlush flush_;
   // A program for copying a source texture into a destination texture.
   ScopedProgram program_;
   // The buffer that holds the vertices and the texture coordinates data for
   // drawing a quad.
   ScopedBuffer vertex_attributes_buffer_;
   ScopedBuffer flipped_vertex_attributes_buffer_;
 
   // The location of the position in the program.
   WebKit::WGC3Dint position_location_;
   // The location of the texture coordinate in the program.
   WebKit::WGC3Dint texcoord_location_;
   // The location of the source texture in the program.
   WebKit::WGC3Dint texture_location_;
   // The location of the texture coordinate of the sub-rectangle in the program.
   WebKit::WGC3Dint src_subrect_location_;
-  std::queue<scoped_refptr<Request> > request_queue_;
+  std::queue<Request*> request_queue_;
 };
 
 const WebKit::WGC3Dfloat GLHelper::CopyTextureToImpl::kVertexAttributes[] = {
   -1.0f, -1.0f, 0.0f, 0.0f,
   1.0f, -1.0f, 1.0f, 0.0f,
   -1.0f, 1.0f, 0.0f, 1.0f,
   1.0f, 1.0f, 1.0f, 1.0f,
 };
 
 const WebKit::WGC3Dfloat
 GLHelper::CopyTextureToImpl::kFlippedVertexAttributes[] = {
   -1.0f, -1.0f, 0.0f, 1.0f,
   1.0f, -1.0f, 1.0f, 1.0f,
   -1.0f, 1.0f, 0.0f, 0.0f,
   1.0f, 1.0f, 1.0f, 0.0f,
 };
 
 const WebKit::WGC3Dchar GLHelper::CopyTextureToImpl::kCopyVertexShader[] =
     "attribute vec2 a_position;"
     "attribute vec2 a_texcoord;"
     "varying vec2 v_texcoord;"
     "uniform vec4 src_subrect;"
     "void main() {"
     "  gl_Position = vec4(a_position, 0.0, 1.0);"
     "  v_texcoord = src_subrect.xy + a_texcoord * src_subrect.zw;"
     "}";
 
+
+#if (SK_R32_SHIFT == 16) && !SK_B32_SHIFT
 const WebKit::WGC3Dchar GLHelper::CopyTextureToImpl::kCopyFragmentShader[] =
     "precision mediump float;"
     "varying vec2 v_texcoord;"
+    "uniform sampler2D s_texture;"
+    "void main() {"
+    "  gl_FragColor = texture2D(s_texture, v_texcoord).bgra;"
+    "}";
+#else
+const WebKit::WGC3Dchar GLHelper::CopyTextureToImpl::kCopyFragmentShader[] =
+    "precision mediump float;"
+    "varying vec2 v_texcoord;"
     "uniform sampler2D s_texture;"
     "void main() {"
     "  gl_FragColor = texture2D(s_texture, v_texcoord);"
     "}";
+#endif
+
 
 void GLHelper::CopyTextureToImpl::InitBuffer() {
   ScopedBufferBinder<GL_ARRAY_BUFFER> buffer_binder(
       context_, vertex_attributes_buffer_);
   context_->bufferData(GL_ARRAY_BUFFER,
                        sizeof(kVertexAttributes),
                        kVertexAttributes,
                        GL_STATIC_DRAW);
   ScopedBufferBinder<GL_ARRAY_BUFFER> flipped_buffer_binder(
       context_, flipped_vertex_attributes_buffer_);
@@ skipping 30 matching lines @@
 
 WebGLId GLHelper::CopyTextureToImpl::ScaleTexture(
     WebGLId src_texture,
     const gfx::Size& src_size,
     const gfx::Rect& src_subrect,
     const gfx::Size& dst_size,
     bool vertically_flip_texture) {
   WebGLId dst_texture = context_->createTexture();
   {
     ScopedFramebuffer dst_framebuffer(context_, context_->createFramebuffer());
-    ScopedFramebufferBinder<GL_FRAMEBUFFER> framebuffer_binder(
-        context_, dst_framebuffer);
+    ScopedFramebufferBinder<GL_FRAMEBUFFER> framebuffer_binder(context_,
+                                                               dst_framebuffer);
     {
-      ScopedTextureBinder<GL_TEXTURE_2D> texture_binder(
-          context_, dst_texture);
+      ScopedTextureBinder<GL_TEXTURE_2D> texture_binder(context_, dst_texture);
       context_->texImage2D(GL_TEXTURE_2D,
                            0,
                            GL_RGBA,
                            dst_size.width(),
                            dst_size.height(),
                            0,
                            GL_RGBA,
                            GL_UNSIGNED_BYTE,
                            NULL);
       context_->framebufferTexture2D(GL_FRAMEBUFFER,
                                      GL_COLOR_ATTACHMENT0,
                                      GL_TEXTURE_2D,
                                      dst_texture,
                                      0);
     }
 
     ScopedTextureBinder<GL_TEXTURE_2D> texture_binder(context_, src_texture);
     WebKit::WebGLId vertex_attributes_buffer = vertically_flip_texture ?
         flipped_vertex_attributes_buffer_ : vertex_attributes_buffer_;
-    ScopedBufferBinder<GL_ARRAY_BUFFER> buffer_binder(
-        context_, vertex_attributes_buffer);
+    ScopedBufferBinder<GL_ARRAY_BUFFER> buffer_binder(context_,
+                                                      vertex_attributes_buffer);
 
     context_->viewport(0, 0, dst_size.width(), dst_size.height());
     context_->useProgram(program_);
 
     WebKit::WGC3Dintptr offset = 0;
     context_->vertexAttribPointer(position_location_,
                                   2,
                                   GL_FLOAT,
                                   GL_FALSE,
                                   4 * sizeof(WebKit::WGC3Dfloat),
@@ skipping 20 matching lines @@
     };
 
     context_->uniform4fv(src_subrect_location_, 1, src_subrect_texcoord);
 
     // Conduct texture mapping by drawing a quad composed of two triangles.
     context_->drawArrays(GL_TRIANGLE_STRIP, 0, 4);
   }
   return dst_texture;
 }
 
-void GLHelper::CopyTextureToImpl::DeleteContextForThread() {
-  if (!context_for_thread_)
-    return;
-
-  g_gl_helper_thread.Pointer()->message_loop_proxy()->PostTask(
-      FROM_HERE,
-      base::Bind(&DeleteContext,
-                 context_for_thread_));
-  context_for_thread_ = NULL;
-}
-
 void GLHelper::CopyTextureToImpl::CropScaleReadbackAndCleanTexture(
     WebGLId src_texture,
     const gfx::Size& src_size,
     const gfx::Rect& src_subrect,
     const gfx::Size& dst_size,
     unsigned char* out,
     const base::Callback<void(bool)>& callback) {
-  if (!context_for_thread_) {
-    callback.Run(false);
-    return;
-  }
-
   WebGLId texture = ScaleTexture(src_texture,
                                  src_size,
                                  src_subrect,
                                  dst_size,
-                                 false);
+#ifdef USE_SKIA
+                                 true
+#else
+                                 false
+#endif
+                                 );
   context_->flush();
-  scoped_refptr<Request> request =
-      new Request(this, texture, dst_size, out, callback);
+  Request* request = new Request(texture, dst_size, out, callback);
   request_queue_.push(request);
+  if (request_queue_.size() == 1) {
+    ScheduleCheckReadbackDone();
+  }
 
-  g_gl_helper_thread.Pointer()->message_loop_proxy()->PostTask(FROM_HERE,
-      base::Bind(&ReadBackFramebuffer,
-                 request,
-                 context_for_thread_,
-                 base::MessageLoopProxy::current()));
+  ScopedFlush flush(context_);
+  ScopedFramebuffer dst_framebuffer(context_, context_->createFramebuffer());
+  gfx::Size size;
+  size = request->size;
+
+  ScopedFramebufferBinder<GL_FRAMEBUFFER> framebuffer_binder(context_,
+                                                             dst_framebuffer);
+  ScopedTextureBinder<GL_TEXTURE_2D> texture_binder(context_, request->texture);
+  context_->framebufferTexture2D(GL_FRAMEBUFFER,
+                                 GL_COLOR_ATTACHMENT0,
+                                 GL_TEXTURE_2D,
+                                 request->texture,
+                                 0);
+  request->buffer = context_->createBuffer();
+  context_->bindBuffer(GL_PIXEL_PACK_TRANSFER_BUFFER_CHROMIUM,
+                       request->buffer);
+  context_->bufferData(GL_PIXEL_PACK_TRANSFER_BUFFER_CHROMIUM,
+                       4 * size.GetArea(),
+                       NULL,
+                       GL_STREAM_READ);
+
+  request->query = context_->createQueryEXT();
+  context_->beginQueryEXT(GL_COMMANDS_ISSUED_CHROMIUM, request->query);
+  context_->readPixels(0, 0, size.width(), size.height(),
+                       GL_RGBA, GL_UNSIGNED_BYTE, 0);
+  context_->endQueryEXT(GL_COMMANDS_ISSUED_CHROMIUM);
+  context_->bindBuffer(GL_PIXEL_PACK_TRANSFER_BUFFER_CHROMIUM, 0);
+
 }
 
 void GLHelper::CopyTextureToImpl::ReadbackTextureSync(WebGLId texture,
                                                       const gfx::Rect& src_rect,
                                                       unsigned char* out) {
   ScopedFramebuffer dst_framebuffer(context_, context_->createFramebuffer());
-  ScopedFramebufferBinder<GL_FRAMEBUFFER> framebuffer_binder(
-      context_, dst_framebuffer);
+  ScopedFramebufferBinder<GL_FRAMEBUFFER> framebuffer_binder(context_,
+                                                             dst_framebuffer);
   ScopedTextureBinder<GL_TEXTURE_2D> texture_binder(context_, texture);
   context_->framebufferTexture2D(GL_FRAMEBUFFER,
                                  GL_COLOR_ATTACHMENT0,
                                  GL_TEXTURE_2D,
                                  texture,
                                  0);
   context_->readPixels(src_rect.x(),
                        src_rect.y(),
                        src_rect.width(),
                        src_rect.height(),
                        GL_RGBA,
                        GL_UNSIGNED_BYTE,
                        out);
 }
 
 WebKit::WebGLId GLHelper::CopyTextureToImpl::CopyAndScaleTexture(
     WebGLId src_texture,
     const gfx::Size& src_size,
     const gfx::Size& dst_size,
     bool vertically_flip_texture) {
   return ScaleTexture(src_texture,
                       src_size,
                       gfx::Rect(src_size),
                       dst_size,
                       vertically_flip_texture);
 }
 
-void GLHelper::CopyTextureToImpl::ReadBackFramebuffer(
-    scoped_refptr<Request> request,
-    WebGraphicsContext3D* context,
-    scoped_refptr<base::TaskRunner> reply_loop) {
-  DCHECK(context);
-  if (!context->makeContextCurrent() || context->isContextLost()) {
-    base::AutoLock auto_lock(request->lock);
-    if (request->pixels) {
-      // Only report failure if the request wasn't canceled (otherwise the
-      // failure has already been reported).
-      request->pixels = NULL;
-      reply_loop->PostTask(
-          FROM_HERE, base::Bind(ReadBackFramebufferComplete, request, false));
-    }
-    return;
-  }
-  ScopedFlush flush(context);
-  ScopedFramebuffer dst_framebuffer(context, context->createFramebuffer());
-  unsigned char* pixels = NULL;
-  gfx::Size size;
-  {
-    // Note: We don't want to keep the lock while doing the readBack (since we
-    // don't want to block the UI thread). We rely on the fact that once the
-    // texture is bound to a FBO (that isn't current), deleting the texture is
-    // delayed until the FBO is deleted. We ensure ordering by flushing while
-    // the lock is held. Either the main thread cancelled before we get the
-    // lock, and we'll exit early, or we ensure that the texture is bound to the
-    // framebuffer before the main thread has a chance to delete it.
-    base::AutoLock auto_lock(request->lock);
-    if (!request->texture || !request->pixels)
-      return;
-    pixels = request->pixels;
-    request->pixels = NULL;
-    size = request->size;
-    {
-      ScopedFlush flush(context);
-      ScopedFramebufferBinder<GL_FRAMEBUFFER> framebuffer_binder(
-          context, dst_framebuffer);
-      ScopedTextureBinder<GL_TEXTURE_2D> texture_binder(
-          context, request->texture);
-      context->framebufferTexture2D(GL_FRAMEBUFFER,
-                                    GL_COLOR_ATTACHMENT0,
-                                    GL_TEXTURE_2D,
-                                    request->texture,
-                                    0);
-    }
-  }
-  bool result = context->readBackFramebuffer(
-        pixels,
-        4 * size.GetArea(),
-        dst_framebuffer.id(),
-        size.width(),
-        size.height());
-  reply_loop->PostTask(
-      FROM_HERE, base::Bind(ReadBackFramebufferComplete, request, result));
+
+void GLHelper::CopyTextureToImpl::ScheduleCheckReadbackDone() {
+  DCHECK(!request_queue_.empty());
+  base::MessageLoopProxy::current()->PostDelayedTask(
+      FROM_HERE,
+      base::Bind(&CopyTextureToImpl::CheckReadbackDone, AsWeakPtr()),
+      base::TimeDelta::FromMilliseconds(2));
 }
 
-void GLHelper::CopyTextureToImpl::ReadBackFramebufferComplete(
-    scoped_refptr<Request> request,
-    bool result) {
-  request->callback.Run(result);
-  if (request->copy_texture_impl)
-    request->copy_texture_impl->FinishRequest(request);
+void GLHelper::CopyTextureToImpl::CheckReadbackDone() {
+  TRACE_EVENT0("mirror",
+               "GLHelper::CopyTextureToImpl::CheckReadBackFramebufferComplete");
+  while (!request_queue_.empty()) {
+    Request* request = request_queue_.front();
+
+    bool result = false;
+    if (request->buffer != 0) {
+      unsigned int done = 1;
+      context_->getQueryObjectuivEXT(request->query,
+                                     GL_QUERY_RESULT_AVAILABLE_EXT, &done);
+      if (!done) {
+        ScheduleCheckReadbackDone();
+        return;
+      }
+      context_->bindBuffer(GL_PIXEL_PACK_TRANSFER_BUFFER_CHROMIUM,
+                           request->buffer);
+      void* data = context_->mapBufferCHROMIUM(
+          GL_PIXEL_PACK_TRANSFER_BUFFER_CHROMIUM, GL_READ_ONLY);
+
+      if (data) {
+        result = true;
+        memcpy(request->pixels, data, request->size.GetArea() * 4);
+        context_->unmapBufferCHROMIUM(GL_PIXEL_PACK_TRANSFER_BUFFER_CHROMIUM);
+      }
+      context_->bindBuffer(GL_PIXEL_PACK_TRANSFER_BUFFER_CHROMIUM, 0);
+    }
+
+    FinishRequest(request, result);
+  }
 }
 
-void GLHelper::CopyTextureToImpl::FinishRequest(
-    scoped_refptr<Request> request) {
-  CHECK(request_queue_.front() == request);
+void GLHelper::CopyTextureToImpl::FinishRequest(Request* request, bool result) {
+  DCHECK(request_queue_.front() == request);
   request_queue_.pop();
-  base::AutoLock auto_lock(request->lock);
+  request->callback.Run(result);
+  ScopedFlush flush(context_);
   if (request->texture != 0) {
     context_->deleteTexture(request->texture);
     request->texture = 0;
-    context_->flush();
   }
+  if (request->buffer != 0) {
+    context_->deleteBuffer(request->buffer);
+    request->buffer = 0;
+  }
+  if (request->query != 0) {
+    context_->deleteQueryEXT(request->query);
+    request->query = 0;
+  }
+  delete request;
 }
 
 void GLHelper::CopyTextureToImpl::CancelRequests() {
   while (!request_queue_.empty()) {
-    scoped_refptr<Request> request = request_queue_.front();
-    request_queue_.pop();
-    request->copy_texture_impl = NULL;
-    bool cancelled = false;
-    {
-      base::AutoLock auto_lock(request->lock);
-      if (request->texture != 0) {
-        context_->deleteTexture(request->texture);
-        request->texture = 0;
-      }
-      if (request->pixels != NULL) {
-        request->pixels = NULL;
-        cancelled = true;
-      }
-    }
-    if (cancelled)
-      request->callback.Run(false);
+    Request* request = request_queue_.front();
+    FinishRequest(request, false);
   }
 }
 
-base::subtle::Atomic32 GLHelper::count_ = 0;
-
-GLHelper::GLHelper(WebGraphicsContext3D* context,
-                   WebGraphicsContext3D* context_for_thread)
-    : context_(context),
-      context_for_thread_(context_for_thread) {
-  base::subtle::NoBarrier_AtomicIncrement(&count_, 1);
+GLHelper::GLHelper(WebGraphicsContext3D* context)
+    : context_(context) {
 }
 
 GLHelper::~GLHelper() {
-  DCHECK_NE(MessageLoop::current(),
-            g_gl_helper_thread.Pointer()->message_loop());
-  base::subtle::Atomic32 decremented_count =
-    base::subtle::NoBarrier_AtomicIncrement(&count_, -1);
-  if (decremented_count == 0) {
-    // When this is the last instance, we synchronize with the pending
-    // operations on GLHelperThread. Otherwise on shutdown we may kill the GPU
-    // process infrastructure (BrowserGpuChannelHostFactory) before they have
-    // a chance to complete, likely leading to a crash.
-    base::WaitableEvent event(false, false);
-    g_gl_helper_thread.Pointer()->message_loop_proxy()->PostTask(
-        FROM_HERE,
-        base::Bind(&SignalWaitableEvent,
-                   &event));
-    // http://crbug.com/125415
-    base::ThreadRestrictions::ScopedAllowWait allow_wait;
-    event.Wait();
-  }
 }
 
 WebGraphicsContext3D* GLHelper::context() const {
   return context_;
 }
 
 void GLHelper::CropScaleReadbackAndCleanTexture(
     WebGLId src_texture,
     const gfx::Size& src_size,
     const gfx::Rect& src_subrect,
@@ skipping 49 matching lines @@
   if (!compile_status) {
     LOG(ERROR) << std::string(context_->getShaderInfoLog(shader).utf8());
     return 0;
   }
   return shader.Detach();
 }
 
 void GLHelper::InitCopyTextToImpl() {
   // Lazily initialize |copy_texture_to_impl_|
   if (!copy_texture_to_impl_.get())
-    copy_texture_to_impl_.reset(new CopyTextureToImpl(context_,
-                                                      context_for_thread_,
-                                                      this));
+    copy_texture_to_impl_.reset(new CopyTextureToImpl(context_, this));
 }
 
 void GLHelper::CopySubBufferDamage(WebKit::WebGLId texture,
                                    WebKit::WebGLId previous_texture,
                                    const SkRegion& new_damage,
                                    const SkRegion& old_damage) {
   SkRegion region(old_damage);
   if (region.op(new_damage, SkRegion::kDifference_Op)) {
     ScopedFramebuffer dst_framebuffer(context_, context_->createFramebuffer());
-    ScopedFramebufferBinder<GL_FRAMEBUFFER> framebuffer_binder(
-        context_, dst_framebuffer);
+    ScopedFramebufferBinder<GL_FRAMEBUFFER> framebuffer_binder(context_,
+                                                               dst_framebuffer);
     ScopedTextureBinder<GL_TEXTURE_2D> texture_binder(context_, texture);
     context_->framebufferTexture2D(GL_FRAMEBUFFER,
                                    GL_COLOR_ATTACHMENT0,
                                    GL_TEXTURE_2D,
                                    previous_texture,
                                    0);
     for (SkRegion::Iterator it(region); !it.done(); it.next()) {
       const SkIRect& rect = it.rect();
       context_->copyTexSubImage2D(GL_TEXTURE_2D, 0,
                                   rect.x(), rect.y(),
                                   rect.x(), rect.y(),
                                   rect.width(), rect.height());
     }
     context_->flush();
   }
 }
 
 }  // namespace content