Add generated and hand-written passthrough command handlers with stub Doers.

gpu/command_buffer/common/buffer.h

Index: gpu/command_buffer/common/buffer.h
diff --git a/gpu/command_buffer/common/buffer.h b/gpu/command_buffer/common/buffer.h
index 0aea591f716bcb7e1ff5455df36348ab0cd1888b..180779317b6bed74f424c01c5fb6213df3d3ade8 100644
--- a/gpu/command_buffer/common/buffer.h
+++ b/gpu/command_buffer/common/buffer.h
@@ -56,6 +56,12 @@ class GPU_EXPORT Buffer : public base::RefCountedThreadSafe<Buffer> {
   // Returns NULL if the address overflows the memory.
   void* GetDataAddress(uint32_t data_offset, uint32_t data_size) const;
 
+  // Returns NULL if the address overflows the memory.
+  void* GetDataAddressAndSize(uint32_t data_offset, uint32_t* data_size) const;
+
+  // Returns the remaining size of the buffer after an offset
+  uint32_t GetRemainingSize(uint32_t data_offset) const;
+
  private:
   friend class base::RefCountedThreadSafe<Buffer>;
   ~Buffer();