Allow task pools to reason about transparency.

cc/raster/tile_task_runner.h

 // Copyright 2014 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 CC_RASTER_TILE_TASK_RUNNER_H_
 #define CC_RASTER_TILE_TASK_RUNNER_H_
 
 #include <bitset>
 #include <vector>
 
@@ skipping 131 matching lines @@
   // Previously scheduled tasks that are not in |queue| will be canceled unless
   // already running. Once scheduled, reply callbacks are guaranteed to run for
   // all tasks even if they later get canceled by another call to
   // ScheduleTasks().
   virtual void ScheduleTasks(TileTaskQueue* queue) = 0;
 
   // Check for completed tasks and dispatch reply callbacks.
   virtual void CheckForCompletedTasks() = 0;
 
   // Returns the format to use for the tiles.
-  virtual ResourceFormat GetResourceFormat() const = 0;
+  virtual ResourceFormat GetResourceFormat(bool must_support_alpha) const = 0;

[reveman, 2015/09/22 14:18:49]

This looks good for now. What do you think about adding something like this in
the future:

enum ResourceFormatDescription {
  COLOR,
  COLOR_AND_ALPHA,
  UNCOMPRESSED_COLOR_AND_ALPHA
};

[christiank, 2015/09/23 12:29:11]

I like it! Much better than the old "two boolean parameters approach" that I
suggested a while back.

 
   // Determine if the resource requires swizzling.
-  virtual bool GetResourceRequiresSwizzle() const = 0;
+  virtual bool GetResourceRequiresSwizzle(bool must_support_alpha) const = 0;
 
  protected:
   virtual ~TileTaskRunner() {}
 };
 
 }  // namespace cc
 
 #endif  // CC_RASTER_TILE_TASK_RUNNER_H_