cc: Add trace output for individual DisplayItems

cc/resources/float_clip_display_item.cc

Index: cc/resources/float_clip_display_item.cc
diff --git a/cc/resources/float_clip_display_item.cc b/cc/resources/float_clip_display_item.cc
index 259ccc88d7018a4ea86cd299276133277368d484..0cfe4635286da2fbe74773f96e9a3ef143ee0f2f 100644
--- a/cc/resources/float_clip_display_item.cc
+++ b/cc/resources/float_clip_display_item.cc
@@ -4,6 +4,8 @@
 
 #include "cc/resources/float_clip_display_item.h"
 
+#include "base/strings/stringprintf.h"
+#include "base/trace_event/trace_event_argument.h"
 #include "third_party/skia/include/core/SkCanvas.h"
 #include "ui/gfx/skia_util.h"
 
@@ -34,6 +36,11 @@ size_t FloatClipDisplayItem::PictureMemoryUsage() const {
   return sizeof(gfx::RectF);
 }
 
+void FloatClipDisplayItem::AsValueInto(base::debug::TracedValue* array) const {
+  array->AppendString(base::StringPrintf("FloatClipDisplayItem rect: [%s]",

[pdr., 2015/02/02 22:22:16]

This is another case I don't think will work in json.

+                                         clip_rect_.ToString().c_str()));
+}
+
 EndFloatClipDisplayItem::EndFloatClipDisplayItem() {
 }
 
@@ -57,4 +64,9 @@ size_t EndFloatClipDisplayItem::PictureMemoryUsage() const {
   return 0;
 }
 
+void EndFloatClipDisplayItem::AsValueInto(
+    base::debug::TracedValue* array) const {
+  array->AppendString("EndFloatClipDisplayItem");
+}
+
 }  // namespace cc