Install a hook to swap between SkPicture backends with a single define.

BUG=skia:
R=robertphillips@google.com, reed@google.com, mtklein@google.com

Author: mtklein@chromium.org

Review URL: https://codereview.chromium.org/492023002
diff --git a/tests/CanvasTest.cpp b/tests/CanvasTest.cpp
index 217cf03..5d6a8d8 100644
--- a/tests/CanvasTest.cpp
+++ b/tests/CanvasTest.cpp
@@ -687,13 +687,13 @@
         // are flattened during the second execution
         testStep->setAssertMessageFormat(kPictureDrawAssertMessageFormat);
         SkPictureRecorder referenceRecorder;
-        SkCanvas* referenceCanvas = referenceRecorder.beginRecording(kWidth, kHeight,
-                                                                     NULL, recordFlags);
+        SkCanvas* referenceCanvas =
+            referenceRecorder.DEPRECATED_beginRecording(kWidth, kHeight, NULL, recordFlags);
         testStep->draw(referenceCanvas, reporter);
 
         SkPictureRecorder testRecorder;
-        SkCanvas* testCanvas = testRecorder.beginRecording(kWidth, kHeight,
-                                                           NULL, recordFlags);
+        SkCanvas* testCanvas =
+            testRecorder.DEPRECATED_beginRecording(kWidth, kHeight, NULL, recordFlags);
         testStep->draw(testCanvas, reporter);
         testStep->setAssertMessageFormat(kPictureSecondDrawAssertMessageFormat);
         testStep->draw(testCanvas, reporter);