replace flaky DCHECK in DrawingBuffer with early-out

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 5ac50c4acb226cae15258341c1da6907b007fa0c..1ee06eaa4f2d596e3f6552850e0dc7bc7112c810 100644
--- a/third_party/WebKit/Source/platform/graphics/gpu/DrawingBuffer.cpp
+++ b/third_party/WebKit/Source/platform/graphics/gpu/DrawingBuffer.cpp
@@ -713,7 +713,10 @@ bool DrawingBuffer::copyToPlatformTexture(gpu::gles2::GLES2Interface* gl,
     m_gl->GenSyncTokenCHROMIUM(fenceSync, produceSyncToken.GetData());
   }
 
-  DCHECK(produceSyncToken.HasData());
+  if (!produceSyncToken.HasData()) {

[Ken Russell (switch to Gerrit), 2016/12/09 21:23:49]

Please add a comment that this should really only happen if the context's been
lost. Unfortunately, I think it would be too flaky to add a DCHECK here that
m_gl->GetGraphicsResetStatusKHR() != NO_ERROR. The specification of this
extension only guarantees that the lost context notification is delivered once.

+    return false;
+  }
+
   gl->WaitSyncTokenCHROMIUM(produceSyncToken.GetConstData());
   GLuint sourceTexture =
       gl->CreateAndConsumeTextureCHROMIUM(target, mailbox.name);