cc: Add UMA for tracking decode duration for out of raster decodes.

cc/tiles/image_decode_cache.h

 // Copyright 2015 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_TILES_IMAGE_DECODE_CACHE_H_
 #define CC_TILES_IMAGE_DECODE_CACHE_H_
 
 #include "base/memory/ref_counted.h"
+#include "cc/base/devtools_instrumentation.h"
 #include "cc/paint/draw_image.h"
 #include "cc/tiles/decoded_draw_image.h"
 #include "cc/tiles/tile_priority.h"
 
 namespace cc {
 
 class TileTask;
 
 // ImageDecodeCache is responsible for generating decode tasks, decoding
 // images, storing images in cache, and being able to return the decoded images
 // when requested.
 
 // ImageDecodeCache is responsible for the following things:
 // 1. Given a DrawImage, it can return an TileTask which when run will
 //    decode and cache the resulting image. If the image does not need a task to
 //    be decoded, then nullptr will be returned. The return value of the
 //    function indicates whether the image was or is going to be locked, so an
 //    unlock will be required.
 // 2. Given a cache key and a DrawImage, it can decode the image and store it in
 //    the cache. Note that it is important that this function is only accessed
 //    via an image decode task.
 // 3. Given a DrawImage, it can return a DecodedDrawImage, which represented the
 //    decoded version of the image. Note that if the image is not in the cache
 //    and it needs to be scaled/decoded, then this decode will happen as part of
 //    getting the image. As such, this should only be accessed from a raster
 //    thread.
 class CC_EXPORT ImageDecodeCache {
  public:
+  enum class ImageDecodeType {
+    IN_RASTER,

[danakj, 2017/05/26 22:36:23]

enums should be kFoo style now

[Khushal, 2017/05/26 23:17:35]

Done.

+    OUT_OF_RASTER_CHECKER_IMAGING,
+    OUT_OF_RASTER_JS_DECODE
+  };
+
+  static devtools_instrumentation::ScopedImageDecodeTask::DecodeTaskType
+  ToScopedDecodeTaskType(ImageDecodeType decode_type) {
+    using ScopedTaskType =
+        devtools_instrumentation::ScopedImageDecodeTask::DecodeTaskType;
+    switch (decode_type) {
+      case ImageDecodeType::IN_RASTER:
+        return ScopedTaskType::IN_RASTER;
+      case ImageDecodeType::OUT_OF_RASTER_CHECKER_IMAGING:
+        return ScopedTaskType::CHECKER_IMAGING;

[danakj, 2017/05/26 22:36:23]

I think itd be less confusing if these names matched maybe?

[Khushal, 2017/05/26 23:17:35]

Done.

+      case ImageDecodeType::OUT_OF_RASTER_JS_DECODE:
+        return ScopedTaskType::JS_DECODE_API;
+    }
+    NOTREACHED();
+    return ScopedTaskType::IN_RASTER;
+  }
+
   // This information should be used strictly in tracing, UMA, and any other
   // reporting systems.
   struct TracingInfo {

[danakj, 2017/05/26 22:36:23]

With these changes, this struct now has 4 constructors.
a) Can we not mix overloading + default values?
b) Do we need so many?

[Khushal, 2017/05/26 23:17:35]

I just removed both.

     TracingInfo(uint64_t prepare_tiles_id,
-                TilePriority::PriorityBin requesting_tile_bin)
+                TilePriority::PriorityBin requesting_tile_bin,
+                ImageDecodeType type = ImageDecodeType::IN_RASTER)
         : prepare_tiles_id(prepare_tiles_id),
-          requesting_tile_bin(requesting_tile_bin) {}
+          requesting_tile_bin(requesting_tile_bin),
+          type(type) {}
     TracingInfo() : TracingInfo(0, TilePriority::NOW) {}
+    explicit TracingInfo(ImageDecodeType type)
+        : TracingInfo(0, TilePriority::NOW, type) {}
 
     // ID for the current prepare tiles call.
     const uint64_t prepare_tiles_id;
 
     // The bin of the tile that caused this image to be requested.
     const TilePriority::PriorityBin requesting_tile_bin;
+
+    // The task type for in-raster and out of raster decode tasks.
+    const ImageDecodeType type;
   };
 
   virtual ~ImageDecodeCache() {}
 
   // Fill in an TileTask which will decode the given image when run. In
   // case the image is already cached, fills in nullptr. Returns true if the
   // image needs to be unreffed when the caller is finished with it.
   //
   // This is called by the tile manager (on the compositor thread) when creating
   // a raster task.
   virtual bool GetTaskForImageAndRef(const DrawImage& image,
                                      const TracingInfo& tracing_info,
                                      scoped_refptr<TileTask>* task) = 0;
   // Similar to GetTaskForImageAndRef, except that it returns tasks that are not
   // meant to be run as part of raster. That is, this is part of a predecode
   // API. Note that this should only return a task responsible for decoding (and
   // not uploading), since it will be run on a worker thread which may not have
   // the right GPU context for upload.
   virtual bool GetOutOfRasterDecodeTaskForImageAndRef(
       const DrawImage& image,
+      ImageDecodeType decode_type,
       scoped_refptr<TileTask>* task) = 0;
 
   // Unrefs an image. When the tile is finished, this should be called for every
   // GetTaskForImageAndRef call that returned true.
   virtual void UnrefImage(const DrawImage& image) = 0;
 
   // Returns a decoded draw image. This may cause a decode if the image was not
   // predecoded.
   //
   // This is called by a raster task (on a worker thread) when an image is
@@ skipping 19 matching lines @@
   // Returns the maximum amount of memory we would be able to lock. This ignores
   // any temporary states, such as throttled, and return the maximum possible
   // memory. It is used as an esimate of whether an image can fit into the
   // locked budget before creating a task.
   virtual size_t GetMaximumMemoryLimitBytes() const = 0;
 };
 
 }  // namespace cc
 
 #endif  // CC_TILES_IMAGE_DECODE_CACHE_H_