[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/services/surfaceflinger/DisplayHardware/HWComposer.cpp b/services/surfaceflinger/DisplayHardware/HWComposer.cpp
index a752a7d..b27344d 100644
--- a/services/surfaceflinger/DisplayHardware/HWComposer.cpp
+++ b/services/surfaceflinger/DisplayHardware/HWComposer.cpp
@@ -756,6 +756,20 @@
     return NO_ERROR;
 }
 
+status_t HWComposer::setDisplayContentSamplingEnabled(DisplayId displayId, bool enabled,
+                                                      uint8_t componentMask, uint64_t maxFrames) {
+    RETURN_IF_INVALID_DISPLAY(displayId, BAD_INDEX);
+    const auto error =
+            mDisplayData[displayId].hwcDisplay->setDisplayContentSamplingEnabled(enabled,
+                                                                                 componentMask,
+                                                                                 maxFrames);
+
+    if (error == HWC2::Error::Unsupported) RETURN_IF_HWC_ERROR(error, displayId, INVALID_OPERATION);
+    if (error == HWC2::Error::BadParameter) RETURN_IF_HWC_ERROR(error, displayId, BAD_VALUE);
+    RETURN_IF_HWC_ERROR(error, displayId, UNKNOWN_ERROR);
+    return NO_ERROR;
+}
+
 bool HWComposer::isUsingVrComposer() const {
     return getComposer()->isUsingVrComposer();
 }