Cache output Framebuffer for RenderEngine::drawLayers

GL comp is now fast.

Also:
* Add additional ATRACE_CALLs
* Remove some todos that we might not get to/are obsolete

Bug: 123107664
Change-Id: I8649e074f8234ccaeb28bb2be6c11a380a808d8f
Test: systrace
diff --git a/libs/renderengine/gl/GLESRenderEngine.cpp b/libs/renderengine/gl/GLESRenderEngine.cpp
index 3d6ac8f..8f9071e 100644
--- a/libs/renderengine/gl/GLESRenderEngine.cpp
+++ b/libs/renderengine/gl/GLESRenderEngine.cpp
@@ -424,6 +424,7 @@
         mTraceGpuCompletion = true;
         mFlushTracer = std::make_unique<FlushTracer>(this);
     }
+    mDrawingBuffer = createFramebuffer();
 }
 
 GLESRenderEngine::~GLESRenderEngine() {
@@ -439,6 +440,10 @@
     return std::make_unique<GLImage>(*this);
 }
 
+Framebuffer* GLESRenderEngine::getFramebufferForDrawing() {
+    return mDrawingBuffer.get();
+}
+
 void GLESRenderEngine::primeCache() const {
     ProgramCache::getInstance().primeCache(mInProtectedContext ? mProtectedEGLContext : mEGLContext,
                                            mFeatureFlags & USE_COLOR_MANAGEMENT);
@@ -678,6 +683,7 @@
 }
 
 void GLESRenderEngine::evictImages(const std::vector<LayerSettings>& layers) {
+    ATRACE_CALL();
     // destroy old image references that we're not going to draw with.
     std::unordered_set<uint64_t> bufIds;
     for (auto layer : layers) {
@@ -744,6 +750,7 @@
 }
 
 void GLESRenderEngine::unbindFrameBuffer(Framebuffer* /* framebuffer */) {
+    ATRACE_CALL();
     mFboHeight = 0;
 
     // back to main framebuffer