Add gpu command buffer support for loseContextCHROMIUM

cc/layers/texture_layer.cc

Index: cc/layers/texture_layer.cc
diff --git a/cc/layers/texture_layer.cc b/cc/layers/texture_layer.cc
index 4266718daaec2b885b96292fdc85fed6e34199a7..d4e63759514cdbabd06029a0469a027302c3a13f 100644
--- a/cc/layers/texture_layer.cc
+++ b/cc/layers/texture_layer.cc
@@ -62,7 +62,7 @@ TextureLayer::~TextureLayer() {
   if (layer_tree_host()) {
     if (texture_id_)
       layer_tree_host()->AcquireLayerTextures();
-    if (rate_limit_context_ && client_)
+    if (rate_limit_context_ && client_ && client_->Context3d())
       layer_tree_host()->StopRateLimiter(client_->Context3d());
   }
   if (own_mailbox_)
@@ -125,7 +125,8 @@ void TextureLayer::SetPremultipliedAlpha(bool premultiplied_alpha) {
 }
 
 void TextureLayer::SetRateLimitContext(bool rate_limit) {
-  if (!rate_limit && rate_limit_context_ && client_ && layer_tree_host())
+  if (!rate_limit && rate_limit_context_ && client_ && client_->Context3d() &&
+      layer_tree_host())
     layer_tree_host()->StopRateLimiter(client_->Context3d());
 
   rate_limit_context_ = rate_limit;
@@ -163,7 +164,8 @@ void TextureLayer::WillModifyTexture() {
 void TextureLayer::SetNeedsDisplayRect(const gfx::RectF& dirty_rect) {
   Layer::SetNeedsDisplayRect(dirty_rect);
 
-  if (rate_limit_context_ && client_ && layer_tree_host() && DrawsContent())
+  if (rate_limit_context_ && client_ && client_->Context3d() &&

[Justin Novosad, 2013/06/21 18:24:11]

I was getting test crashes right here because of lack of NULL ptr check after
context loss.  The other similar checks I added in this file are speculative. 
Do you think they are necessary?

[piman, 2013/06/21 19:05:05]

Why is the context NULL after a context loss?
Losing the context doesn't mean the context has to become NULL. It's the
responsibility of the client to keep the context around....

+      layer_tree_host() && DrawsContent())
     layer_tree_host()->StartRateLimiter(client_->Context3d());
 }
 
@@ -190,6 +192,7 @@ void TextureLayer::Update(ResourceUpdateQueue* queue,
       texture_id_ = client_->PrepareTexture(queue);
     }
     context_lost_ =
+        !client_->Context3d() ||
         client_->Context3d()->getGraphicsResetStatusARB() != GL_NO_ERROR;
   }