Add SF side tunnel mode listener

This CL adds a TunnelModeStateReporter, which monitors if there are
any layers with a sideband stream in SurfaceFlinger. If any of the
layers have a sideband stream, it informs all the registered listeners
that tunnel mode is enabled. When no layers have a sideband stream, it
notifies the listeners that tunnel mode is disabled.

Bug: 171457637
Test: atest TunnelModeStateListenerTest
Test: atest TunnelModeStateReporterTest
Change-Id: Ie54b34dbd9b6253d7142e9b0f690c8469374604d
diff --git a/services/surfaceflinger/TunnelModeEnabledReporter.h b/services/surfaceflinger/TunnelModeEnabledReporter.h
new file mode 100644
index 0000000..d55507a
--- /dev/null
+++ b/services/surfaceflinger/TunnelModeEnabledReporter.h
@@ -0,0 +1,66 @@
+/*
+ * Copyright 2021 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#pragma once
+
+#include <android-base/thread_annotations.h>
+#include <android/gui/ITunnelModeEnabledListener.h>
+#include <binder/IBinder.h>
+
+#include <unordered_map>
+
+namespace android {
+
+class Layer;
+class SurfaceFlinger;
+
+class TunnelModeEnabledReporter : public IBinder::DeathRecipient {
+public:
+    TunnelModeEnabledReporter(SurfaceFlinger& flinger);
+
+    // Checks if there is a tunnel mode enabled state change and if so, dispatches the updated
+    // tunnel mode enabled/disabled state to the registered listeners
+    // This method performs layer stack traversals, so mStateLock must be held when calling this
+    // method.
+    void updateTunnelModeStatus();
+
+    // Dispatches tunnelModeEnabled to all registered listeners
+    void dispatchTunnelModeEnabled(bool tunnelModeEnabled);
+
+    // Override for IBinder::DeathRecipient
+    void binderDied(const wp<IBinder>&) override;
+
+    // Registers a TunnelModeEnabled listener
+    void addListener(const sp<gui::ITunnelModeEnabledListener>& listener);
+
+    // Deregisters a TunnelModeEnabled listener
+    void removeListener(const sp<gui::ITunnelModeEnabledListener>& listener);
+
+private:
+    mutable std::mutex mMutex;
+    struct WpHash {
+        size_t operator()(const wp<IBinder>& p) const {
+            return std::hash<IBinder*>()(p.unsafe_get());
+        }
+    };
+
+    SurfaceFlinger& mFlinger;
+    std::unordered_map<wp<IBinder>, sp<gui::ITunnelModeEnabledListener>, WpHash> mListeners
+            GUARDED_BY(mMutex);
+    bool mTunnelModeEnabled GUARDED_BY(mMutex) = false;
+};
+
+} // namespace android