Implement SkiaGLRenderEngine::cleanFramebufferCache

On hotplug SF calls cleanFramebufferCache in order to
clean the existing handles to framebuffers. This CL
implements the function for SkiaGLRenderEngine and
fixes a bug where after each hotplug we end up with
+3 framebuffers.

Fixes: 182578852
Test: manually flash build, hotplug and call
      adb shell dumpsys SurfaceFlinger | grep Framebuffer
      to verify that only 3 framebuffers are present

Change-Id: I2a0d1ab6005e3c7a994f8c8c0eeec79afc96d109
diff --git a/libs/renderengine/skia/SkiaGLRenderEngine.cpp b/libs/renderengine/skia/SkiaGLRenderEngine.cpp
index cbb02a3..acd3dcf 100644
--- a/libs/renderengine/skia/SkiaGLRenderEngine.cpp
+++ b/libs/renderengine/skia/SkiaGLRenderEngine.cpp
@@ -293,11 +293,9 @@
 }
 
 SkiaGLRenderEngine::~SkiaGLRenderEngine() {
-    std::lock_guard<std::mutex> lock(mRenderingMutex);
-    mRuntimeEffects.clear();
-    mProtectedTextureCache.clear();
-    mTextureCache.clear();
+    cleanFramebufferCache();
 
+    std::lock_guard<std::mutex> lock(mRenderingMutex);
     if (mBlurFilter) {
         delete mBlurFilter;
     }
@@ -1130,7 +1128,14 @@
     return eglCreatePbufferSurface(display, placeholderConfig, attributes.data());
 }
 
-void SkiaGLRenderEngine::cleanFramebufferCache() {}
+void SkiaGLRenderEngine::cleanFramebufferCache() {
+    // TODO(b/180767535) Remove this method and use b/180767535 instead, which would allow
+    // SF to control texture lifecycle more tightly rather than through custom hooks into RE.
+    std::lock_guard<std::mutex> lock(mRenderingMutex);
+    mRuntimeEffects.clear();
+    mProtectedTextureCache.clear();
+    mTextureCache.clear();
+}
 
 int SkiaGLRenderEngine::getContextPriority() {
     int value;