Initialize local variables to avoid data leak

The uninitialized local variables pick up
whatever the memory content was there on stack.
This data gets sent to the remote process in
case of a failed transaction, which is a security
issue. Fixed.

(Partial manual merge of master change
 12ba0f57d028a9c8f4eb3afddc326b70677d1e0c. Rest
 to automerge from klp-dev)

For b/23696300

Change-Id: I704c9fab327b3545c58e8a9a96ac542eb7469c2a

libs/gui/IGraphicBufferProducer.cpp

@@ -389,7 +389,7 @@ status_t BnGraphicBufferProducer::onTransact(
             CHECK_INTERFACE(IGraphicBufferProducer, data, reply);
             sp<GraphicBuffer> buffer = new GraphicBuffer();
             data.read(*buffer.get());
-            int slot;
+            int slot = 0;
             int result = attachBuffer(&slot, buffer);
             reply->writeInt32(slot);
             reply->writeInt32(result);