Ignore custom offscreen surface unless explicitly opted in

content/renderer/renderer_blink_platform_impl.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/renderer/renderer_blink_platform_impl.h"
 
 #include <memory>
 #include <utility>
 
 #include "base/command_line.h"
@@ skipping 969 matching lines @@
   // This is an offscreen context. Generally it won't use the default
   // frame buffer, in that case don't request any alpha, depth, stencil,
   // antialiasing. But we do need those attributes for the "own
   // offscreen surface" optimization which supports directly drawing
   // to a custom surface backed frame buffer.
   gpu::gles2::ContextCreationAttribHelper attributes;
   attributes.alpha_size = web_attributes.supportAlpha ? 8 : -1;
   attributes.depth_size = web_attributes.supportDepth ? 24 : 0;
   attributes.stencil_size = web_attributes.supportStencil ? 8 : 0;
   attributes.samples = web_attributes.supportAntialias ? 4 : 0;
+  attributes.own_offscreen_surface =
+      web_attributes.supportAlpha || web_attributes.supportDepth ||
+      web_attributes.supportStencil || web_attributes.supportAntialias;
   attributes.sample_buffers = 0;
   attributes.bind_generates_resource = false;
   // Prefer discrete GPU for WebGL.
   attributes.gpu_preference = gl::PreferDiscreteGpu;
 
   attributes.fail_if_major_perf_caveat =
       web_attributes.failIfMajorPerformanceCaveat;
   DCHECK_GT(web_attributes.webGLVersion, 0u);
   DCHECK_LE(web_attributes.webGLVersion, 2u);
   if (web_attributes.webGLVersion == 2)
@@ skipping 256 matching lines @@
 //------------------------------------------------------------------------------
 void RendererBlinkPlatformImpl::requestPurgeMemory() {
   // TODO(tasak|bashi): We should use ChildMemoryCoordinator here, but
   // ChildMemoryCoordinator isn't always available as it's only initialized
   // when kMemoryCoordinatorV0 is enabled.
   // Use ChildMemoryCoordinator when memory coordinator is always enabled.
   base::MemoryCoordinatorClientRegistry::GetInstance()->PurgeMemory();
 }
 
 }  // namespace content