Add calls to EnsureGPUMemoryAvailable into GLES2DecoderImpl

gpu/command_buffer/service/memory_tracking.h

Index: gpu/command_buffer/service/memory_tracking.h
diff --git a/gpu/command_buffer/service/memory_tracking.h b/gpu/command_buffer/service/memory_tracking.h
index 155ed4b5aa2f219ac97ee95ccb15484176a39515..49a9960e12183f3370b396bc9b7d7b22ad0b1dbd 100644
--- a/gpu/command_buffer/service/memory_tracking.h
+++ b/gpu/command_buffer/service/memory_tracking.h
@@ -25,6 +25,9 @@ class MemoryTracker : public base::RefCounted<MemoryTracker> {
                                            size_t new_size,
                                            Pool pool) = 0;
 
+   // Ensure a certain amount of GPU memory is free. Returns true on success.
+   virtual bool EnsureGPUMemoryAvailable(size_t size_needed) = 0;
+
  protected:
   friend class base::RefCounted<MemoryTracker>;
   MemoryTracker() {}