Optimizations for TLHC frame rate and jank (#50033)

- ImageReaderSurfaceProducer no longer drops frames when the producer
and the consumers are up to two frames out of sync.
- Have the native C++ side of the Android external textures check if a
new frame has been pushed and that the texture needs to be updated. This
avoids having to schedule a task on the raster thread for each updated
texture.
- Notify the engine earlier that a frame is needed when updating a TLHC
texture.

Author: johnmccutchan

shell/platform/android/android_shell_holder_unittests.cc

@@ -35,6 +35,10 @@ class MockPlatformViewAndroidJNI : public PlatformViewAndroidJNI {
               SurfaceTextureAttachToGLContext,
               (JavaLocalRef surface_texture, int textureId),
               (override));
+  MOCK_METHOD(bool,
+              SurfaceTextureShouldUpdate,
+              (JavaLocalRef surface_texture),
+              (override));
   MOCK_METHOD(void,
               SurfaceTextureUpdateTexImage,
               (JavaLocalRef surface_texture),

shell/platform/android/image_external_texture.cc

@@ -26,11 +26,9 @@ void ImageExternalTexture::Paint(PaintContext& context,
     return;
   }
   Attach(context);
-  const bool should_process_frame =
-      (!freeze && new_frame_ready_) || dl_image_ == nullptr;
+  const bool should_process_frame = !freeze;
   if (should_process_frame) {
     ProcessFrame(context, bounds);
-    new_frame_ready_ = false;
   }
   if (dl_image_) {
     context.canvas->DrawImageRect(
@@ -48,7 +46,7 @@ void ImageExternalTexture::Paint(PaintContext& context,
 
 // Implementing flutter::Texture.
 void ImageExternalTexture::MarkNewFrameAvailable() {
-  new_frame_ready_ = true;
+  // NOOP.
 }
 
 // Implementing flutter::Texture.

shell/platform/android/image_external_texture.h

@@ -61,7 +61,6 @@ class ImageExternalTexture : public flutter::Texture {
 
   enum class AttachmentState { kUninitialized, kAttached, kDetached };
   AttachmentState state_ = AttachmentState::kUninitialized;
-  bool new_frame_ready_ = false;
 
   sk_sp<flutter::DlImage> dl_image_;
 

shell/platform/android/io/flutter/embedding/engine/FlutterJNI.java

@@ -951,6 +951,16 @@ public void markTextureFrameAvailable(long textureId) {
 
   private native void nativeMarkTextureFrameAvailable(long nativeShellHolderId, long textureId);
 
+  /** Schedule the engine to draw a frame but does not invalidate the layout tree. */
+  @UiThread
+  public void scheduleFrame() {
+    ensureRunningOnMainThread();
+    ensureAttachedToNative();
+    nativeScheduleFrame(nativeShellHolderId);
+  }
+
+  private native void nativeScheduleFrame(long nativeShellHolderId);
+
   /**
    * Unregisters a texture that was registered with {@link #registerTexture(long,
    * SurfaceTextureWrapper)}.