cc: Add command line switch to control resource usage for impl-side painting.

cc/resources/resource_pool.h

Index: cc/resources/resource_pool.h
diff --git a/cc/resources/resource_pool.h b/cc/resources/resource_pool.h
index f8f52ac701e30f34b6634329df7cbf46909d87af..a73207a3c9f4bcb40e2180a9a1cbf42dd26674df 100644
--- a/cc/resources/resource_pool.h
+++ b/cc/resources/resource_pool.h
@@ -42,15 +42,21 @@ class CC_EXPORT ResourcePool {
       const gfx::Size&, GLenum format);
   void ReleaseResource(scoped_ptr<ResourcePool::Resource>);
 
-  void SetMaxMemoryUsageBytes(size_t max_memory_usage_bytes);
+  void SetMaxMemoryUsageBytes(
+      size_t max_memory_usage_bytes,
+      size_t max_unused_memory_usage_bytes);
 
  protected:
   explicit ResourcePool(ResourceProvider* resource_provider);
 
+  bool MemoryUsageTooHigh();
+
  private:
   ResourceProvider* resource_provider_;
   size_t max_memory_usage_bytes_;
+  size_t max_unused_memory_usage_bytes_;
   size_t memory_usage_bytes_;
+  size_t unused_memory_usage_bytes_;
 
   typedef std::list<Resource*> ResourceList;
   ResourceList resources_;