return reference to cache instead of copying the mask

src/core/SkMask.cpp

Index: src/core/SkMask.cpp
diff --git a/src/core/SkMask.cpp b/src/core/SkMask.cpp
index 4ae65c7a9cc871b64952e7e90c8a295f9855e43f..111508074a3e7f34cc2849ac77609eee0efce49e 100644
--- a/src/core/SkMask.cpp
+++ b/src/core/SkMask.cpp
@@ -7,6 +7,8 @@
 
 #include "SkMask.h"
 
+//#define TRACK_SKMASK_LIFETIME
+
 /** returns the product if it is positive and fits in 31 bits. Otherwise this
     returns 0.
  */
@@ -30,10 +32,17 @@ size_t SkMask::computeTotalImageSize() const {
     return size;
 }
 
+#ifdef TRACK_SKMASK_LIFETIME
+    static int gCounter;
+#endif
+
 /** We explicitly use this allocator for SkBimap pixels, so that we can
     freely assign memory allocated by one class to the other.
 */
 uint8_t* SkMask::AllocImage(size_t size) {
+#ifdef TRACK_SKMASK_LIFETIME
+    SkDebugf("SkMask::AllocImage %d\n", gCounter++);
+#endif
     return (uint8_t*)sk_malloc_throw(SkAlign4(size));
 }
 
@@ -41,6 +50,11 @@ uint8_t* SkMask::AllocImage(size_t size) {
     freely assign memory allocated by one class to the other.
 */
 void SkMask::FreeImage(void* image) {
+#ifdef TRACK_SKMASK_LIFETIME
+    if (image) {
+        SkDebugf("SkMask::FreeImage  %d\n", --gCounter);
+    }
+#endif
     sk_free(image);
 }