cc: Add traces for identification of raster buffer.

cc/raster/gpu_raster_buffer_provider.cc

Index: cc/raster/gpu_raster_buffer_provider.cc
diff --git a/cc/raster/gpu_raster_buffer_provider.cc b/cc/raster/gpu_raster_buffer_provider.cc
index 95bf983ae2ae4016725f6469b26c0a0ede457d06..6e5b4c472a0db7c62290e3a1279d9a34da77404b 100644
--- a/cc/raster/gpu_raster_buffer_provider.cc
+++ b/cc/raster/gpu_raster_buffer_provider.cc
@@ -44,7 +44,7 @@ class RasterBufferImpl : public RasterBuffer {
       uint64_t new_content_id,
       float scale,
       const RasterSource::PlaybackSettings& playback_settings) override {
-    TRACE_EVENT0("cc", "RasterBufferImpl::Playback");
+    TRACE_EVENT0("cc", "GpuRasterBuffer::Playback");
     // GPU raster doesn't do low res tiles, so should always include images.
     DCHECK(!playback_settings.skip_images);