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, 3 deletions

diff --git a/src/gpu/SkGpuDevice.cpp b/src/gpu/SkGpuDevice.cpp
index 9518600e99..eee93bb0c7 100644
--- a/src/gpu/SkGpuDevice.cpp
+++ b/src/gpu/SkGpuDevice.cpp
@@ -2014,9 +2014,10 @@ bool SkGpuDevice::EXPERIMENTAL_drawPicture(SkCanvas* mainCanvas, const SkPicture
         return false;
     }
 
-    SkPicture::AccelData::Key key = SkLayerInfo::ComputeKey();
-
-    const SkPicture::AccelData* data = mainPicture->EXPERIMENTAL_getAccelData(key);
+    const SkBigPicture::AccelData* data = NULL;
+    if (const SkBigPicture* bp = mainPicture->asSkBigPicture()) {
+        data = bp->accelData();
+    }
     if (!data) {
         return false;
     }