Fix for native crash on image decode OOM

When decoding an image with scaling, if the allocation of the bitmap
data for the scaled bitmap failed, we were just ignoring it and going
on. This was yielding strange native crashes (bug 7196860 and bug
7175536). This patch checks whether the allocation succeeds, and returns
a null bitmap if not.

Of course, if the app really is OOM because it's allocated too many
bitmaps, it'll still get the OOME, but that's a lot nicer than a native
crash or memory corruption.

Change-Id: I8384059ab11c2ab9e93e283b9438d79e6709b7b1

Author: raphlinus

core/jni/android/graphics/BitmapFactory.cpp

@@ -340,7 +340,9 @@ static jobject doDecode(JNIEnv* env, SkStream* stream, jobject padding,
 
         bitmap->setConfig(config, scaledWidth, scaledHeight);
         bitmap->setIsOpaque(decoded->isOpaque());
-        bitmap->allocPixels(&javaAllocator, NULL);
+        if (!bitmap->allocPixels(&javaAllocator, NULL)) {
+            return nullObjectReturn("allocation failed for scaled bitmap");
+        }
         bitmap->eraseColor(0);
 
         SkPaint paint;