Add auto purging for SkPicture-related Ganesh resources (esp. layers)

tools/PictureBenchmark.cpp

Index: tools/PictureBenchmark.cpp
diff --git a/tools/PictureBenchmark.cpp b/tools/PictureBenchmark.cpp
index 70ce180dac9761a8c4e1aedc96fbd9b5c32556de..e2a726f1a51a9cce6a0965e0fc39891927a03b06 100644
--- a/tools/PictureBenchmark.cpp
+++ b/tools/PictureBenchmark.cpp
@@ -81,12 +81,6 @@ void PictureBenchmark::run(SkPicture* pict) {
     fRenderer->render(NULL);
     fRenderer->resetState(true);   // flush, swapBuffers and Finish
 
-    if (fPreprocess) {
-        if (NULL != fRenderer->getCanvas()) {
-            fRenderer->getCanvas()->EXPERIMENTAL_purge(pict);
-        }
-    }
-
     if (fPurgeDecodedTex) {
         fRenderer->purgeTextures();
     }
@@ -220,12 +214,6 @@ void PictureBenchmark::run(SkPicture* pict) {
 
                 SkAssertResult(perRunTimerData.appendTimes(perRunTimer.get()));
 
-                if (fPreprocess) {
-                    if (NULL != fRenderer->getCanvas()) {
-                        fRenderer->getCanvas()->EXPERIMENTAL_purge(pict);
-                    }
-                }
-
                 if (fPurgeDecodedTex) {
                     fRenderer->purgeTextures();
                 }