Make sure SkDrawLooper objects can only be allocated on the heap.

Make constructors of SkLayerDrawLooper and SkBlurDrawLooper non-public.
Remove addLayer* methods from SkLayerDrawLooper. SkLayerDrawLooper::Builder is
used to create new objects.
Provide factory method for creating SkBlurDrawLooper.

BUG=2141
R=scroggo@google.com, reed@google.com, djsollen@google.com

Author: dominikg@chromium.org

Review URL: https://codereview.chromium.org/232913003

git-svn-id: http://skia.googlecode.com/svn/trunk@14200 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/gm/blurroundrect.cpp b/gm/blurroundrect.cpp
index 6c3903f..f688380 100644
--- a/gm/blurroundrect.cpp
+++ b/gm/blurroundrect.cpp
@@ -53,7 +53,7 @@
     }
 
     virtual void onDraw(SkCanvas* canvas) SK_OVERRIDE {
-        SkLayerDrawLooper* looper = new SkLayerDrawLooper;
+        SkLayerDrawLooper::Builder looperBuilder;
         {
             SkLayerDrawLooper::LayerInfo info;
             info.fPaintBits = SkLayerDrawLooper::kMaskFilter_Bit
@@ -61,7 +61,7 @@
             info.fColorMode = SkXfermode::kSrc_Mode;
             info.fOffset = SkPoint::Make(SkIntToScalar(-1), SkIntToScalar(0));
             info.fPostTranslate = false;
-            SkPaint* paint = looper->addLayerOnTop(info);
+            SkPaint* paint = looperBuilder.addLayerOnTop(info);
             SkMaskFilter* maskFilter = SkBlurMaskFilter::Create(
                     SkBlurMaskFilter::kNormal_BlurStyle,
                     SkBlurMask::ConvertRadiusToSigma(SK_ScalarHalf),
@@ -74,12 +74,12 @@
         }
         {
             SkLayerDrawLooper::LayerInfo info;
-            looper->addLayerOnTop(info);
+            looperBuilder.addLayerOnTop(info);
         }
         SkPaint paint;
         canvas->drawRect(fRRect.rect(), paint);
 
-        paint.setLooper(looper)->unref();
+        paint.setLooper(looperBuilder.detachLooper())->unref();
         paint.setColor(SK_ColorCYAN);
         paint.setAntiAlias(true);