add basic tests for save/restore counting

BUG=skia:

Review URL: https://codereview.chromium.org/763503003

src/core/SkCanvas.cpp

@@ -811,6 +811,36 @@ void SkCanvas::updateDeviceCMCache() {
 
 ///////////////////////////////////////////////////////////////////////////////
 
+int SkCanvas::getSaveCount() const {
+    return fMCStack.count();
+}
+
+int SkCanvas::save() {
+    this->willSave();
+    return this->internalSave();
+}
+
+void SkCanvas::restore() {
+    // check for underflow
+    if (fMCStack.count() > 1) {
+        this->willRestore();
+        this->internalRestore();
+        this->didRestore();
+    }
+}
+
+void SkCanvas::restoreToCount(int count) {
+    // sanity check
+    if (count < 1) {
+        count = 1;
+    }
+    
+    int n = this->getSaveCount() - count;
+    for (int i = 0; i < n; ++i) {
+        this->restore();
+    }
+}
+
 int SkCanvas::internalSave() {
     int saveCount = this->getSaveCount(); // record this before the actual save
 
@@ -823,11 +853,6 @@ int SkCanvas::internalSave() {
     return saveCount;
 }
 
-int SkCanvas::save() {
-    this->willSave();
-    return this->internalSave();
-}
-
 static bool bounds_affects_clip(SkCanvas::SaveFlags flags) {
 #ifdef SK_SUPPORT_LEGACY_CLIPTOLAYERFLAG
     return (flags & SkCanvas::kClipToLayer_SaveFlag) != 0;
@@ -977,15 +1002,6 @@ int SkCanvas::saveLayerAlpha(const SkRect* bounds, U8CPU alpha,
     }
 }
 
-void SkCanvas::restore() {
-    // check for underflow
-    if (fMCStack.count() > 1) {
-        this->willRestore();
-        this->internalRestore();
-        this->didRestore();
-    }
-}
-
 void SkCanvas::internalRestore() {
     SkASSERT(fMCStack.count() != 0);
 
@@ -1023,22 +1039,6 @@ void SkCanvas::internalRestore() {
     }
 }
 
-int SkCanvas::getSaveCount() const {
-    return fMCStack.count();
-}
-
-void SkCanvas::restoreToCount(int count) {
-    // sanity check
-    if (count < 1) {
-        count = 1;
-    }
-
-    int n = this->getSaveCount() - count;
-    for (int i = 0; i < n; ++i) {
-        this->restore();
-    }
-}
-
 bool SkCanvas::isDrawingToLayer() const {
     return fSaveLayerCount > 0;
 }

tests/CanvasTest.cpp

@@ -795,3 +795,21 @@ DEF_TEST(Canvas, reporter) {
 
     test_newraster(reporter);
 }
+
+DEF_TEST(Canvas_SaveState, reporter) {
+    SkCanvas canvas(10, 10);
+    REPORTER_ASSERT(reporter, 1 == canvas.getSaveCount());
+
+    int n = canvas.save();
+    REPORTER_ASSERT(reporter, 1 == n);
+    REPORTER_ASSERT(reporter, 2 == canvas.getSaveCount());
+
+    n = canvas.saveLayer(NULL, NULL);
+    REPORTER_ASSERT(reporter, 2 == n);
+    REPORTER_ASSERT(reporter, 3 == canvas.getSaveCount());
+    
+    canvas.restore();
+    REPORTER_ASSERT(reporter, 2 == canvas.getSaveCount());
+    canvas.restore();
+    REPORTER_ASSERT(reporter, 1 == canvas.getSaveCount());
+}