Allow WebExternalTextureLayers to receive a bitmap along with a mailbox

cc/layers/texture_layer.cc

 // Copyright 2010 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 "cc/layers/texture_layer.h"
 
 #include "cc/base/thread.h"
 #include "cc/layers/texture_layer_client.h"
 #include "cc/layers/texture_layer_impl.h"
 #include "cc/trees/layer_tree_host.h"
@@ skipping 141 matching lines @@
   SetNeedsCommit();
 }
 
 void TextureLayer::WillModifyTexture() {
   if (layer_tree_host() && (DrawsContent() || content_committed_)) {
     layer_tree_host()->AcquireLayerTextures();
     content_committed_ = false;
   }
 }
 
+bool TextureLayer::MustUseSharedMemory() {
+  return !layer_tree_host()->UsingGLRenderer();

[piman, 2013/07/01 22:45:01]

note: layer_tree_host() is NULL when the layer is outside of the tree.
More generally we may construct layer trees before we know anything about the
system capabilities. I'm not sure UsingGLRenderer() is generally safe.

Maybe a better way would be to pass that info through PrepareTextureMailbox - I
believe that's the only place you need it currently. PrepareTextureMailbox is
called from TextureLayer::Update which is called from
LayerTreeHost::UpdateLayers, which has 2 advantages:
1- you know for sure you have a LTH
2- LTH::UpdateLayers is called from the BeginFrame flow, i.e. started from the
proxy/LTHI after proper initialization, when we have all the information (i.e.
similar to, say, the max texture size).

[jbauman, 2013/07/02 00:00:40]

Ok, modified PrepareTextureMailbox to do this instead.

+}
+
 void TextureLayer::SetNeedsDisplayRect(const gfx::RectF& dirty_rect) {
   Layer::SetNeedsDisplayRect(dirty_rect);
 
   if (rate_limit_context_ && client_ && layer_tree_host() && DrawsContent())
     layer_tree_host()->StartRateLimiter(client_->Context3d());
 }
 
 void TextureLayer::SetLayerTreeHost(LayerTreeHost* host) {
   if (texture_id_ && layer_tree_host() && host != layer_tree_host())
     layer_tree_host()->AcquireLayerTextures();
@@ skipping 79 matching lines @@
 TextureLayer::MailboxHolder::~MailboxHolder() {
   mailbox_.RunReleaseCallback(sync_point_, is_lost_);
 }
 
 void TextureLayer::MailboxHolder::Return(unsigned sync_point, bool is_lost) {
   sync_point_ = sync_point;
   is_lost_ = is_lost;
 }
 
 }  // namespace cc