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

cc/tiles/image_decode_cache.h

Index: cc/tiles/image_decode_cache.h
diff --git a/cc/tiles/image_decode_cache.h b/cc/tiles/image_decode_cache.h
index 1b550a6b06e411718ea04d79d05d4cd6f351251d..fc304d40b647f410c08fee1e7091ad519d705551 100644
--- a/cc/tiles/image_decode_cache.h
+++ b/cc/tiles/image_decode_cache.h
@@ -6,6 +6,7 @@
 #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"
@@ -34,20 +35,49 @@ class TileTask;
 //    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() {}
@@ -68,6 +98,7 @@ class CC_EXPORT ImageDecodeCache {
   // 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