CanvasState frame init refactor

bug:23760482

Change-Id: Idc0802b4b8a6a3cebd20797350f4eb01bcc3fe77
diff --git a/libs/hwui/CanvasState.cpp b/libs/hwui/CanvasState.cpp
index e307ad9..c128ca7 100644
--- a/libs/hwui/CanvasState.cpp
+++ b/libs/hwui/CanvasState.cpp
@@ -34,12 +34,17 @@
 
 }
 
-CanvasState::~CanvasState() {
-
-}
-
-void CanvasState::initializeSaveStack(float clipLeft, float clipTop,
+void CanvasState::initializeSaveStack(
+        int viewportWidth, int viewportHeight,
+        float clipLeft, float clipTop,
         float clipRight, float clipBottom, const Vector3& lightCenter) {
+    if (mWidth != viewportWidth || mHeight != viewportHeight) {
+        mWidth = viewportWidth;
+        mHeight = viewportHeight;
+        mFirstSnapshot->initializeViewport(viewportWidth, viewportHeight);
+        mCanvas.onViewportInitialized();
+    }
+
     mSnapshot = new Snapshot(mFirstSnapshot,
             SkCanvas::kMatrix_SaveFlag | SkCanvas::kClip_SaveFlag);
     mSnapshot->setClip(clipLeft, clipTop, clipRight, clipBottom);
@@ -48,20 +53,6 @@
     mSaveCount = 1;
 }
 
-void CanvasState::setViewport(int width, int height) {
-    mWidth = width;
-    mHeight = height;
-    mFirstSnapshot->initializeViewport(width, height);
-    mCanvas.onViewportInitialized();
-
-    // create a temporary 1st snapshot, so old snapshots are released,
-    // and viewport can be queried safely.
-    // TODO: remove, combine viewport + save stack initialization
-    mSnapshot = new Snapshot(mFirstSnapshot,
-            SkCanvas::kMatrix_SaveFlag | SkCanvas::kClip_SaveFlag);
-    mSaveCount = 1;
-}
-
 ///////////////////////////////////////////////////////////////////////////////
 // Save (layer)
 ///////////////////////////////////////////////////////////////////////////////