Revert of Sketch splitting SkPicture into an interface and SkBigPicture.

src/gpu/SkGpuDevice.cpp

Index: src/gpu/SkGpuDevice.cpp
diff --git a/src/gpu/SkGpuDevice.cpp b/src/gpu/SkGpuDevice.cpp
index 25f6fd370f57240865ed40db98401af13a6a955a..7b363635e29369306f8eb49dbd0ec4b5bcb11b15 100644
--- a/src/gpu/SkGpuDevice.cpp
+++ b/src/gpu/SkGpuDevice.cpp
@@ -1999,10 +1999,9 @@
         return false;
     }
 
-    const SkBigPicture::AccelData* data = NULL;
-    if (const SkBigPicture* bp = mainPicture->asSkBigPicture()) {
-        data = bp->accelData();
-    }
+    SkPicture::AccelData::Key key = SkLayerInfo::ComputeKey();
+
+    const SkPicture::AccelData* data = mainPicture->EXPERIMENTAL_getAccelData(key);
     if (!data) {
         return false;
     }