[SurfaceFlinger] add setDisplayContentSamplingEnabled i/f

Add interface to ISurfaceComposer that can enable or disable
the graphics.composer's collection of the displayed content
statistics.

Bug: 116028618
Test: Boot
Test: ran test client against prototype, see enable/disable working.
Test: Ran new tests './libgui_test --gtest_filter="DisplayedContentSamp*"'
Test: on hwc with and without new function hook.
Change-Id: Ifb487e2bfbd8e0db6178ccbf762aa968c34576b9
diff --git a/libs/gui/SurfaceComposerClient.cpp b/libs/gui/SurfaceComposerClient.cpp
index 9dfccc7..405d228 100644
--- a/libs/gui/SurfaceComposerClient.cpp
+++ b/libs/gui/SurfaceComposerClient.cpp
@@ -1098,6 +1098,14 @@
                                                     outComponentMask);
 }
 
+status_t SurfaceComposerClient::setDisplayContentSamplingEnabled(const sp<IBinder>& display,
+                                                                 bool enable, uint8_t componentMask,
+                                                                 uint64_t maxFrames) {
+    return ComposerService::getComposerService()->setDisplayContentSamplingEnabled(display, enable,
+                                                                                   componentMask,
+                                                                                   maxFrames);
+}
+
 // ----------------------------------------------------------------------------
 
 status_t ScreenshotClient::capture(const sp<IBinder>& display, const ui::Dataspace reqDataSpace,