Fix a bug in drawBuffers optimization.

gpu/command_buffer/service/framebuffer_manager.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef GPU_COMMAND_BUFFER_SERVICE_FRAMEBUFFER_MANAGER_H_
 #define GPU_COMMAND_BUFFER_SERVICE_FRAMEBUFFER_MANAGER_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 176 matching lines @@
   // Checks if a draw buffer's format and its corresponding fragment shader
   // output's type are compatible, i.e., a signed integer typed variable is
   // incompatible with a float or unsigned integer buffer.
   // Return false if incompaticle.
   // Otherwise, filter out the draw buffers that are not written to but are not
   // NONE through DrawBuffers, to be on the safe side. Return true.
   // This is applied before a draw call.
   bool ValidateAndAdjustDrawBuffers(uint32_t fragment_output_type_mask,
                                     uint32_t fragment_output_written_mask);
 
+  // Filter out the draw buffers that have no images attached but are not NONE
+  // through DrawBuffers, to be on the safe side.
+  // This is applied before a clear call.
+  void AdjustDrawBuffers();
+
   bool ContainsActiveIntegerAttachments() const;
 
   // Return true if any draw buffers has an alpha channel.
   bool HasAlphaMRT() const;
 
   // Return false if any two active color attachments have different internal
   // formats.
   bool HasSameInternalFormatsMRT() const;
 
   void set_read_buffer(GLenum read_buffer) {
@@ skipping 33 matching lines @@
 
   unsigned framebuffer_complete_state_count_id() const {
     return framebuffer_complete_state_count_id_;
   }
 
   // Cache color attachments' base type mask (FLOAT, INT, UINT) and bound mask.
   // If an attachment point has no image, it's set as UNDEFINED_TYPE.
   // This call is only valid on a complete fbo.
   void UpdateDrawBufferMasks();
 
+  // Helper for ValidateAndAdjustDrawBuffers() and AdjustDrawBuffers().
+  void AdjustDrawBuffersImpl(uint32_t desired_mask);
+
   // The managers that owns this.
   FramebufferManager* manager_;
 
   bool deleted_;
 
   // Service side framebuffer id.
   GLuint service_id_;
 
   // Whether this framebuffer has ever been bound.
   bool has_been_bound_;
@@ skipping 112 matching lines @@
 
   scoped_refptr<FramebufferCompletenessCache> framebuffer_combo_complete_cache_;
 
   DISALLOW_COPY_AND_ASSIGN(FramebufferManager);
 };
 
 }  // namespace gles2
 }  // namespace gpu
 
 #endif  // GPU_COMMAND_BUFFER_SERVICE_FRAMEBUFFER_MANAGER_H_