[SurfaceFlinger] add getDisplayedContentSample i/f

Add interface to ISurfaceComposer that can query the
graphics.composer for statistics on the displayed pixel content.

Bug: 116028618
Test: Boot
Test: ran test client, see data collected
Change-Id: Ide9b81b80c3399e7d648c7b611514e0d699120de
diff --git a/libs/gui/tests/DisplayedContentSampling_test.cpp b/libs/gui/tests/DisplayedContentSampling_test.cpp
index f9d5dd6..5443812 100644
--- a/libs/gui/tests/DisplayedContentSampling_test.cpp
+++ b/libs/gui/tests/DisplayedContentSampling_test.cpp
@@ -104,4 +104,19 @@
                                                                0);
     EXPECT_EQ(OK, status);
 }
+
+TEST_F(DisplayedContentSamplingTest, SampleCollectionCoherentWithSupportMask) {
+    if (shouldSkipTest()) return;
+
+    DisplayedFrameStats stats;
+    status_t status = mComposerClient->getDisplayedContentSample(mDisplayToken, 0, 0, &stats);
+    EXPECT_EQ(OK, status);
+    if (stats.numFrames <= 0) return;
+
+    if (componentMask & (0x1 << 0)) EXPECT_NE(0, stats.component_0_sample.size());
+    if (componentMask & (0x1 << 1)) EXPECT_NE(0, stats.component_1_sample.size());
+    if (componentMask & (0x1 << 2)) EXPECT_NE(0, stats.component_2_sample.size());
+    if (componentMask & (0x1 << 3)) EXPECT_NE(0, stats.component_3_sample.size());
+}
+
 } // namespace android