Rearrange SkRecord public API to fit better with cc/resources/picture

BUG=skia:2378
R=reed@google.com, danakj@chromium.org, enne@chromium.org, mtklein@google.com, robertphillips@google.com

Author: mtklein@chromium.org

Review URL: https://codereview.chromium.org/248033002

git-svn-id: http://skia.googlecode.com/svn/trunk@14351 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/record/SkRecorder.cpp b/src/record/SkRecorder.cpp
index 345597c..fe4f35f 100644
--- a/src/record/SkRecorder.cpp
+++ b/src/record/SkRecorder.cpp
@@ -12,6 +12,10 @@
 SkRecorder::SkRecorder(SkRecorder::Mode mode, SkRecord* record, int width, int height)
     : SkCanvas(width, height), fMode(mode), fRecord(record) {}
 
+void SkRecorder::forgetRecord() {
+    fRecord = NULL;
+}
+
 // To make appending to fRecord a little less verbose.
 #define APPEND(T, ...) \
         SkNEW_PLACEMENT_ARGS(fRecord->append<SkRecords::T>(), SkRecords::T, (__VA_ARGS__))