guarded change to SkImageGenerator to make getInfo() const

src/lazy/SkCachingPixelRef.cpp

Index: src/lazy/SkCachingPixelRef.cpp
diff --git a/src/lazy/SkCachingPixelRef.cpp b/src/lazy/SkCachingPixelRef.cpp
index dc53a5d6c78c7cf651f545a32482d23500d78633..5fc0d2a87fa7180e88ed3404c175ee0750cf2f5e 100644
--- a/src/lazy/SkCachingPixelRef.cpp
+++ b/src/lazy/SkCachingPixelRef.cpp
@@ -11,11 +11,12 @@
 
 bool SkCachingPixelRef::Install(SkImageGenerator* generator,
                                 SkBitmap* dst) {
-    SkImageInfo info;
     SkASSERT(dst != NULL);
-    if ((NULL == generator)
-        || !(generator->getInfo(&info))
-        || !dst->setInfo(info)) {
+    if (NULL == generator) {
+        return false;
+    }
+    const SkImageInfo info = generator->getInfo();
+    if (!dst->setInfo(info)) {
         SkDELETE(generator);
         return false;
     }