Sketch splitting SkPicture into an interface and SkBigPicture.

Adds small pictures for drawRect(), drawTextBlob(), and drawPath().
These cover about 89% of draw calls from Blink SKPs,
and about 25% of draw calls from our GMs.

SkPicture handles:
  - serialization and deserialization
  - unique IDs

Everything else is left to the subclasses:
  - playback(), cullRect()
  - hasBitmap(), hasText(), suitableForGPU(), etc.
  - LayerInfo / AccelData if applicable.

The time to record a 1-op picture improves a good chunk
(2 mallocs to 1), and the time to record a 0-op picture
greatly improves (2 mallocs to none):

    picture_overhead_draw:   450ns -> 350ns
    picture_overhead_nodraw: 300ns -> 90ns

BUG=skia:

Review URL: https://codereview.chromium.org/1112523006

1 files changed, 4 insertions, 1 deletions

diff --git a/tests/GpuLayerCacheTest.cpp b/tests/GpuLayerCacheTest.cpp
index 6b3084b641..efb1ec1c20 100644
--- a/tests/GpuLayerCacheTest.cpp
+++ b/tests/GpuLayerCacheTest.cpp
@@ -111,7 +111,10 @@ DEF_GPUTEST(GpuLayerCache, reporter, factory) {
         }
 
         SkPictureRecorder recorder;
-        recorder.beginRecording(1, 1);
+        SkCanvas* c = recorder.beginRecording(1, 1);
+            // Draw something, anything, to prevent an empty-picture optimization,
+            // which is a singleton and never purged.
+            c->drawRect(SkRect::MakeWH(1,1), SkPaint());
         SkAutoTUnref<const SkPicture> picture(recorder.endRecording());
 
         GrLayerCache cache(context);