BufferQueue improvements and APIs changes

this is the first step of a series of improvements to
BufferQueue. A few things happen in this change:

- setSynchronousMode() goes away as well as the SynchronousModeAllowed flag
- BufferQueue now defaults to (what used to be) synchronous mode
- a new "controlled by app" flag is passed when creating consumers and producers
  those flags are used to put the BufferQueue in a mode where it
  will never block if both flags are set. This is achieved by:
  - returning an error from dequeueBuffer() if it would block
  - making sure a buffer is always available by replacing
    the previous buffer with the new one in queueBuffer()
    (note: this is similar to what asynchrnous mode used to be)

Note: in this change EGL's swap-interval 0 is broken; this will be
fixed in another change.

Change-Id: I691f9507d6e2e158287e3039f2a79a4d4434211d
diff --git a/include/gui/ConsumerBase.h b/include/gui/ConsumerBase.h
index 42b84cc..7b58bc5 100644
--- a/include/gui/ConsumerBase.h
+++ b/include/gui/ConsumerBase.h
@@ -87,7 +87,9 @@
 
     // ConsumerBase constructs a new ConsumerBase object to consume image
     // buffers from the given BufferQueue.
-    ConsumerBase(const sp<BufferQueue> &bufferQueue);
+    // The controlledByApp flag indicates that this consumer is under the application's
+    // control.
+    ConsumerBase(const sp<BufferQueue> &bufferQueue, bool controlledByApp = false);
 
     // onLastStrongRef gets called by RefBase just before the dtor of the most
     // derived class.  It is used to clean up the buffers so that ConsumerBase