libgui/SurfaceFlinger: Add getConsumerName

Adds a getConsumerName method to IGraphicBufferProducer and Surface.
Currently, the name is cached inside of IGBP and is update on connect
and dequeueBuffer, which should be good enough for most uses.

Bug: 6667401
Change-Id: I22c7881d778e495cf8276de7bbcd769e52429915
diff --git a/include/gui/IGraphicBufferProducer.h b/include/gui/IGraphicBufferProducer.h
index 4ca4cd5..9530de1 100644
--- a/include/gui/IGraphicBufferProducer.h
+++ b/include/gui/IGraphicBufferProducer.h
@@ -480,6 +480,9 @@
     // affected and will retain their current generation number. The generation
     // number defaults to 0.
     virtual status_t setGenerationNumber(uint32_t generationNumber) = 0;
+
+    // Returns the name of the connected consumer.
+    virtual String8 getConsumerName() const = 0;
 };
 
 // ----------------------------------------------------------------------------