Fix the compositing of placeholder canvas backgrounds

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

 // Copyright 2016 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 "platform/graphics/OffscreenCanvasFrameDispatcherImpl.h"
 
 #include "cc/output/compositor_frame.h"
 #include "cc/quads/texture_draw_quad.h"
 #include "gpu/command_buffer/client/gles2_interface.h"
 #include "platform/CrossThreadFunctional.h"
@@ skipping 197 matching lines @@
     return;
   }
   cc::CompositorFrame frame;
   // TODO(crbug.com/652931): update the device_scale_factor
   frame.metadata.device_scale_factor = 1.0f;
 
   const gfx::Rect bounds(m_width, m_height);
   const int renderPassId = 1;
   std::unique_ptr<cc::RenderPass> pass = cc::RenderPass::Create();
   pass->SetNew(renderPassId, bounds, bounds, gfx::Transform());
-  pass->has_transparent_background = false;
 
   cc::SharedQuadState* sqs = pass->CreateAndAppendSharedQuadState();
   sqs->SetAll(gfx::Transform(), bounds.size(), bounds, bounds, false, 1.f,
               SkBlendMode::kSrcOver, 0);
 
   cc::TransferableResource resource;
   resource.id = m_nextResourceId;
   resource.format = cc::ResourceFormat::RGBA_8888;
   resource.size = gfx::Size(m_width, m_height);
   // TODO(crbug.com/646022): making this overlay-able.
@@ skipping 36 matching lines @@
   postImageToPlaceholder(std::move(image));
   commitTypeHistogram.count(commitType);
 
   m_nextResourceId++;
   frame.resource_list.push_back(std::move(resource));
 
   cc::TextureDrawQuad* quad =
       pass->CreateAndAppendDrawQuad<cc::TextureDrawQuad>();
   gfx::Size rectSize(m_width, m_height);
 
+  // TODO(crbug.com/705019): optimize for contexts that have {alpha: false}
   const bool needsBlending = true;
+  gfx::Rect opaqueRect(0, 0);
+
   // TOOD(crbug.com/645993): this should be inherited from WebGL context's
   // creation settings.
   const bool premultipliedAlpha = true;
   const gfx::PointF uvTopLeft(0.f, 0.f);
   const gfx::PointF uvBottomRight(1.f, 1.f);
   float vertexOpacity[4] = {1.f, 1.f, 1.f, 1.f};
   // TODO(crbug.com/645994): this should be true when using style
   // "image-rendering: pixelated".
   // TODO(crbug.com/645590): filter should respect the image-rendering CSS
   // property of associated canvas element.
   const bool nearestNeighbor = false;
-  quad->SetAll(sqs, bounds, bounds, bounds, needsBlending, resource.id,
+  quad->SetAll(sqs, bounds, opaqueRect, bounds, needsBlending, resource.id,
                gfx::Size(), premultipliedAlpha, uvTopLeft, uvBottomRight,
                SK_ColorTRANSPARENT, vertexOpacity, yflipped, nearestNeighbor,
                false);
 
   frame.render_pass_list.push_back(std::move(pass));
 
   double elapsedTime = WTF::monotonicallyIncreasingTime() - commitStartTime;
 
   switch (commitType) {
     case CommitGPUCanvasGPUCompositing:
@@ skipping 153 matching lines @@
 
 void OffscreenCanvasFrameDispatcherImpl::reshape(int width, int height) {
   if (m_width != width || m_height != height) {
     m_width = width;
     m_height = height;
     m_changeSizeForNextCommit = true;
   }
 }
 
 }  // namespace blink