use AutoRestore instead of making a copy of the clipstack

BUG=skia:

Change-Id: I86683156926f7c63c83790eaf313112ba5fab763
Reviewed-on: https://skia-review.googlesource.com/9532
Reviewed-by: Florin Malita <fmalita@chromium.org>
Commit-Queue: Mike Reed <reed@google.com>

2 files changed, 22 insertions, 1 deletions

diff --git a/src/core/SkClipStack.h b/src/core/SkClipStack.h
index e889208f47..9360f4de33 100644
--- a/src/core/SkClipStack.h
+++ b/src/core/SkClipStack.h
@@ -341,6 +341,27 @@ public:
     void save();
     void restore();
 
+    class AutoRestore {
+    public:
+        AutoRestore(SkClipStack* cs, bool doSave)
+            : fCS(cs), fSaveCount(cs->getSaveCount())
+        {
+            if (doSave) {
+                fCS->save();
+            }
+        }
+        ~AutoRestore() {
+            SkASSERT(fCS->getSaveCount() >= fSaveCount);  // no underflow
+            while (fCS->getSaveCount() > fSaveCount) {
+                fCS->restore();
+            }
+        }
+
+    private:
+        SkClipStack* fCS;
+        const int    fSaveCount;
+    };
+
     /**
      * getBounds places the current finite bound in its first parameter. In its
      * second, it indicates which kind of bound is being returned. If
diff --git a/src/core/SkClipStackDevice.h b/src/core/SkClipStackDevice.h
index 1dd321d820..916aaf8455 100644
--- a/src/core/SkClipStackDevice.h
+++ b/src/core/SkClipStackDevice.h
@@ -18,7 +18,7 @@ public:
         , fClipStack(fStorage, sizeof(fStorage))
     {}
 
-    const SkClipStack& cs() const { return fClipStack; }
+    SkClipStack& cs() { return fClipStack; }
 
     SkIRect devClipBounds() const;