Revert multiple display support for embedder API (#21456)

This reverts commits
- 67fdd7e.
- 854943d.

See: flutter/flutter#66829

Author: iskakaushik

ci/licenses_golden/licenses_flutter

@@ -599,9 +599,6 @@ FILE: ../../../flutter/shell/common/animator_unittests.cc
 FILE: ../../../flutter/shell/common/canvas_spy.cc
 FILE: ../../../flutter/shell/common/canvas_spy.h
 FILE: ../../../flutter/shell/common/canvas_spy_unittests.cc
-FILE: ../../../flutter/shell/common/display.h
-FILE: ../../../flutter/shell/common/display_manager.cc
-FILE: ../../../flutter/shell/common/display_manager.h
 FILE: ../../../flutter/shell/common/engine.cc
 FILE: ../../../flutter/shell/common/engine.h
 FILE: ../../../flutter/shell/common/engine_unittests.cc

shell/common/BUILD.gn

@@ -64,9 +64,6 @@ source_set("common") {
     "animator.h",
     "canvas_spy.cc",
     "canvas_spy.h",
-    "display.h",
-    "display_manager.cc",
-    "display_manager.h",
     "engine.cc",
     "engine.h",
     "isolate_configuration.cc",

shell/common/animator.cc

@@ -53,6 +53,10 @@ Animator::Animator(Delegate& delegate,
 
 Animator::~Animator() = default;
 
+float Animator::GetDisplayRefreshRate() const {
+  return waiter_->GetDisplayRefreshRate();
+}
+
 void Animator::Stop() {
   paused_ = true;
 }

shell/common/animator.h

@@ -47,6 +47,8 @@ class Animator final {
 
   ~Animator();
 
+  float GetDisplayRefreshRate() const;
+
   void RequestFrame(bool regenerate_layer_tree = true);
 
   void Render(std::unique_ptr<flutter::LayerTree> layer_tree);

shell/common/display.h

@@ -97,6 +97,10 @@ Engine::Engine(Delegate& delegate,
 
 Engine::~Engine() = default;
 
+float Engine::GetDisplayRefreshRate() const {
+  return animator_->GetDisplayRefreshRate();
+}
+
 fml::WeakPtr<Engine> Engine::GetWeakPtr() const {
   return weak_factory_.GetWeakPtr();
 }

shell/common/display_manager.cc

@@ -24,7 +24,6 @@
 #include "flutter/runtime/runtime_controller.h"
 #include "flutter/runtime/runtime_delegate.h"
 #include "flutter/shell/common/animator.h"
-#include "flutter/shell/common/display_manager.h"
 #include "flutter/shell/common/platform_view.h"
 #include "flutter/shell/common/pointer_data_dispatcher.h"
 #include "flutter/shell/common/rasterizer.h"
@@ -329,6 +328,30 @@ class Engine final : public RuntimeDelegate,
   ///
   ~Engine() override;
 
+  //----------------------------------------------------------------------------
+  /// @brief      Gets the refresh rate in frames per second of the vsync waiter
+  ///             used by the animator managed by this engine. This information
+  ///             is purely advisory and is not used by any component. It is
+  ///             only used by the tooling to visualize frame performance.
+  ///
+  /// @attention  The display refresh rate is useless for frame scheduling
+  ///             because it can vary and more accurate frame specific
+  ///             information is given to the engine by the vsync waiter
+  ///             already. However, this call is used by the tooling to ask very
+  ///             high level questions about display refresh rate. For example,
+  ///             "Is the display 60 or 120Hz?". This information is quite
+  ///             unreliable (not available immediately on launch on some
+  ///             platforms), variable and advisory. It must not be used by any
+  ///             component that claims to use it to perform accurate frame
+  ///             scheduling.
+  ///
+  /// @return     The display refresh rate in frames per second. This may change
+  ///             from frame to frame, throughout the lifecycle of the
+  ///             application, and, may not be available immediately upon
+  ///             application launch.
+  ///
+  float GetDisplayRefreshRate() const;
+
   //----------------------------------------------------------------------------
   /// @return     The pointer to this instance of the engine. The engine may
   ///             only be accessed safely on the UI task runner.

shell/common/display_manager.h

@@ -68,9 +68,7 @@ class Rasterizer final : public SnapshotDelegate {
     ///
     virtual void OnFrameRasterized(const FrameTiming& frame_timing) = 0;
 
-    /// Time limit for a smooth frame.
-    ///
-    /// See: `DisplayManager::GetMainDisplayRefreshRate`.
+    /// Time limit for a smooth frame. See `Engine::GetDisplayRefreshRate`.
     virtual fml::Milliseconds GetFrameBudget() = 0;
 
     /// Target time for the latest frame. See also `Shell::OnAnimatorBeginFrame`