camera2: Use valid dimensions for RGBA8888 gralloc buffers.

Bug: 17675571

- All of the mistakes were made.  Unmake them.

Change-Id: I23ff7a553347d4d9588c728219f4bf0604ba2e38
diff --git a/media/jni/android_media_ImageReader.cpp b/media/jni/android_media_ImageReader.cpp
index f4eb459..aaff9a2 100644
--- a/media/jni/android_media_ImageReader.cpp
+++ b/media/jni/android_media_ImageReader.cpp
@@ -294,7 +294,7 @@
     uint8_t* jpegBuffer = buffer->data;
 
     if (usingRGBAOverride) {
-        width *= 4;
+        width = (buffer->width + buffer->stride * (buffer->height - 1)) * 4;
     }
 
     // First check for JPEG transport header at the end of the buffer