cc: Add mailbox support to ResourceProvider write locks.

cc/output/gl_renderer.cc

Index: cc/output/gl_renderer.cc
diff --git a/cc/output/gl_renderer.cc b/cc/output/gl_renderer.cc
index 6a75674271e6921f2f0658f281f12aa86425776e..32f5d36ebcd5725192c1ad83153dfb35175002e2 100644
--- a/cc/output/gl_renderer.cc
+++ b/cc/output/gl_renderer.cc
@@ -841,9 +841,10 @@ std::unique_ptr<ScopedResource> GLRenderer::GetBackdropTexture(
       bounding_rect.size(), ResourceProvider::TEXTURE_HINT_DEFAULT,
       resource_provider_->best_texture_format());
   {
-    ResourceProvider::ScopedWriteLockGL lock(resource_provider_,
-                                             device_background_texture->id());
-    GetFramebufferTexture(lock.texture_id(), RGBA_8888, bounding_rect);
+    ResourceProvider::ScopedWriteLockGL lock(
+        resource_provider_, device_background_texture->id(), false);
+    GetFramebufferTexture(lock.ProduceTextureId(), RGBA_8888, bounding_rect);
+    lock.ReleaseTextureId();
   }
   return device_background_texture;
 }
@@ -2987,10 +2988,11 @@ bool GLRenderer::BindFramebufferToTexture(DrawingFrame* frame,
   gl_->BindFramebuffer(GL_FRAMEBUFFER, offscreen_framebuffer_id_);
   current_framebuffer_lock_ =
       base::WrapUnique(new ResourceProvider::ScopedWriteLockGL(
-          resource_provider_, texture->id()));
-  unsigned texture_id = current_framebuffer_lock_->texture_id();
+          resource_provider_, texture->id(), false));
+  unsigned texture_id = current_framebuffer_lock_->ProduceTextureId();
   gl_->FramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D,
                             texture_id, 0);
+  current_framebuffer_lock_->ReleaseTextureId();
 
   DCHECK(gl_->CheckFramebufferStatus(GL_FRAMEBUFFER) ==
              GL_FRAMEBUFFER_COMPLETE ||