libgui: Normalize IGraphicBufferConsumer methods

This change modifies IGraphicBufferConsumer such that all synchronous
methods return a status_t and, as such, all outputs are returned by
output parameter rather than return value. It also eliminates the use
of a const char* parameter that SafeInterface can't handle.

Test: m -j + libgui_tests + manual testing
Change-Id: I9bb0e2892492d5e0a3f660bf228834b9ed014539
diff --git a/services/surfaceflinger/SurfaceFlingerConsumer.cpp b/services/surfaceflinger/SurfaceFlingerConsumer.cpp
index 1d2b485..9babeef 100644
--- a/services/surfaceflinger/SurfaceFlingerConsumer.cpp
+++ b/services/surfaceflinger/SurfaceFlingerConsumer.cpp
@@ -139,7 +139,9 @@
 }
 
 sp<NativeHandle> SurfaceFlingerConsumer::getSidebandStream() const {
-    return mConsumer->getSidebandStream();
+    sp<NativeHandle> stream;
+    mConsumer->getSidebandStream(&stream);
+    return stream;
 }
 
 // We need to determine the time when a buffer acquired now will be