Revert "Lift restriction that embedders may not trample the render thread OpenGL context in composition callbacks. (#16653)" (#16674)

This reverts commit 110c1c9.

Author: chinmaygarde

ci/licenses_golden/licenses_flutter

@@ -126,8 +126,6 @@ FILE: ../../../flutter/fml/file_unittest.cc
 FILE: ../../../flutter/fml/gpu_thread_merger.cc
 FILE: ../../../flutter/fml/gpu_thread_merger.h
 FILE: ../../../flutter/fml/gpu_thread_merger_unittests.cc
-FILE: ../../../flutter/fml/hash_combine.h
-FILE: ../../../flutter/fml/hash_combine_unittests.cc
 FILE: ../../../flutter/fml/icu_util.cc
 FILE: ../../../flutter/fml/icu_util.h
 FILE: ../../../flutter/fml/log_level.h
@@ -915,20 +913,15 @@ FILE: ../../../flutter/shell/platform/embedder/embedder_engine.cc
 FILE: ../../../flutter/shell/platform/embedder/embedder_engine.h
 FILE: ../../../flutter/shell/platform/embedder/embedder_external_texture_gl.cc
 FILE: ../../../flutter/shell/platform/embedder/embedder_external_texture_gl.h
-FILE: ../../../flutter/shell/platform/embedder/embedder_external_view.cc
-FILE: ../../../flutter/shell/platform/embedder/embedder_external_view.h
 FILE: ../../../flutter/shell/platform/embedder/embedder_external_view_embedder.cc
 FILE: ../../../flutter/shell/platform/embedder/embedder_external_view_embedder.h
 FILE: ../../../flutter/shell/platform/embedder/embedder_include.c
-FILE: ../../../flutter/shell/platform/embedder/embedder_include2.c
 FILE: ../../../flutter/shell/platform/embedder/embedder_layers.cc
 FILE: ../../../flutter/shell/platform/embedder/embedder_layers.h
 FILE: ../../../flutter/shell/platform/embedder/embedder_platform_message_response.cc
 FILE: ../../../flutter/shell/platform/embedder/embedder_platform_message_response.h
 FILE: ../../../flutter/shell/platform/embedder/embedder_render_target.cc
 FILE: ../../../flutter/shell/platform/embedder/embedder_render_target.h
-FILE: ../../../flutter/shell/platform/embedder/embedder_render_target_cache.cc
-FILE: ../../../flutter/shell/platform/embedder/embedder_render_target_cache.h
 FILE: ../../../flutter/shell/platform/embedder/embedder_safe_access.h
 FILE: ../../../flutter/shell/platform/embedder/embedder_surface.cc
 FILE: ../../../flutter/shell/platform/embedder/embedder_surface.h

fml/BUILD.gn

@@ -26,7 +26,6 @@ source_set("fml") {
     "file.h",
     "gpu_thread_merger.cc",
     "gpu_thread_merger.h",
-    "hash_combine.h",
     "icu_util.cc",
     "icu_util.h",
     "log_level.h",
@@ -233,7 +232,6 @@ executable("fml_unittests") {
     "command_line_unittest.cc",
     "file_unittest.cc",
     "gpu_thread_merger_unittests.cc",
-    "hash_combine_unittests.cc",
     "memory/ref_counted_unittest.cc",
     "memory/weak_ptr_unittest.cc",
     "message_loop_task_queues_merge_unmerge_unittests.cc",

fml/hash_combine.h

@@ -26,16 +26,16 @@ class CanvasSpy {
  public:
   CanvasSpy(SkCanvas* target_canvas);
 
-  //----------------------------------------------------------------------------
-  /// @brief      Returns true if any non transparent content has been drawn
+  //------------------------------------------------------------------------------
+  /// @brief      Returns true if any non trasnparent content has been drawn
   /// into
   ///             the spying canvas. Note that this class does tries to detect
   ///             empty canvases but in some cases may return true even for
   ///             empty canvases (e.g when a transparent image is drawn into the
   ///             canvas).
   bool DidDrawIntoCanvas();
 
-  //----------------------------------------------------------------------------
+  //------------------------------------------------------------------------------
   /// @brief      The returned canvas delegate all operations to the target
   /// canvas
   ///             while spying on them.

fml/hash_combine_unittests.cc

@@ -29,20 +29,15 @@ template("embedder_source_set") {
       "embedder_engine.h",
       "embedder_external_texture_gl.cc",
       "embedder_external_texture_gl.h",
-      "embedder_external_view.cc",
-      "embedder_external_view.h",
       "embedder_external_view_embedder.cc",
       "embedder_external_view_embedder.h",
       "embedder_include.c",
-      "embedder_include2.c",
       "embedder_layers.cc",
       "embedder_layers.h",
       "embedder_platform_message_response.cc",
       "embedder_platform_message_response.h",
       "embedder_render_target.cc",
       "embedder_render_target.h",
-      "embedder_render_target_cache.cc",
-      "embedder_render_target_cache.h",
       "embedder_safe_access.h",
       "embedder_surface.cc",
       "embedder_surface.h",