test-hwc2: set layer plane alpha

Test: Add "#define HAVE_NO_SURFACE_FLINGER" to
          frameworks/native/libs/gui/BufferQueueCore.cpp.
      Recompile and flash.
      Run "mm" in frameworks/native/services/surfaceflinger/tests/hwc2.
      Push test-hwc2 to device.
      Run "adb root && adb shell stop".
      Run test case. Ex: "./test-hwc2"

Change-Id: I48146953f745dc650ead5a6e9d6f456cf5a9d7ef
diff --git a/services/surfaceflinger/tests/hwc2/Hwc2TestProperties.h b/services/surfaceflinger/tests/hwc2/Hwc2TestProperties.h
index 236843e..f54c8c8 100644
--- a/services/surfaceflinger/tests/hwc2/Hwc2TestProperties.h
+++ b/services/surfaceflinger/tests/hwc2/Hwc2TestProperties.h
@@ -124,4 +124,17 @@
     static const std::vector<android_dataspace_t> completeDataspaces;
 };
 
+
+class Hwc2TestPlaneAlpha : public Hwc2TestProperty<float> {
+public:
+    Hwc2TestPlaneAlpha(Hwc2TestCoverage coverage);
+
+    std::string dump() const override;
+
+protected:
+    static const std::vector<float> mDefaultPlaneAlphas;
+    static const std::vector<float> mBasicPlaneAlphas;
+    static const std::vector<float> mCompletePlaneAlphas;
+};
+
 #endif /* ifndef _HWC2_TEST_PROPERTIES_H */