Remove return values from clipping operations

bug:22530947

Also switch mode to enum class

Change-Id: Iabb38634c01f2e3203b1b715967d8828d95da190
diff --git a/libs/hwui/CanvasState.cpp b/libs/hwui/CanvasState.cpp
index 54fb5f2..e307ad9 100644
--- a/libs/hwui/CanvasState.cpp
+++ b/libs/hwui/CanvasState.cpp
@@ -155,17 +155,20 @@
 ///////////////////////////////////////////////////////////////////////////////
 
 bool CanvasState::clipRect(float left, float top, float right, float bottom, SkRegion::Op op) {
-    mDirtyClip |= mSnapshot->clip(left, top, right, bottom, op);
+    mSnapshot->clip(left, top, right, bottom, op);
+    mDirtyClip = true;
     return !mSnapshot->clipIsEmpty();
 }
 
 bool CanvasState::clipPath(const SkPath* path, SkRegion::Op op) {
-    mDirtyClip |= mSnapshot->clipPath(*path, op);
+    mSnapshot->clipPath(*path, op);
+    mDirtyClip = true;
     return !mSnapshot->clipIsEmpty();
 }
 
 bool CanvasState::clipRegion(const SkRegion* region, SkRegion::Op op) {
-    mDirtyClip |= mSnapshot->clipRegionTransformed(*region, op);
+    mSnapshot->clipRegionTransformed(*region, op);
+    mDirtyClip = true;
     return !mSnapshot->clipIsEmpty();
 }