[flutter_runner] update CompositorContext for roll

In https://github.com/flutter/engine/pull/9819, support for
merging/unmerging the Flutter GPU thread and platform thread was landed
to support better performance of platform views on iOS. This resulted in
changes to the CompositorContext and ScopedFrame APIs which are also
used by Fuchsia's flutter_runner.

This is a breaking change approved in:
https://bugs.fuchsia.dev/p/fuchsia/issues/detail?id=27323

Change-Id: I2140412ac686842b132c35a7f1300e3ba79e3749
diff --git a/runtime/flutter_runner/compositor_context.cc b/runtime/flutter_runner/compositor_context.cc
index f92e9fc..e14e4e9 100644
--- a/runtime/flutter_runner/compositor_context.cc
+++ b/runtime/flutter_runner/compositor_context.cc
@@ -16,7 +16,7 @@
               SessionConnection& session_connection)
       : flutter::CompositorContext::ScopedFrame(
             context, nullptr, nullptr, nullptr, root_surface_transformation,
-            instrumentation_enabled),
+            instrumentation_enabled, nullptr),
         session_connection_(session_connection) {}
 
  private:
@@ -85,7 +85,8 @@
 CompositorContext::AcquireFrame(GrContext* gr_context, SkCanvas* canvas,
                                 flutter::ExternalViewEmbedder* view_embedder,
                                 const SkMatrix& root_surface_transformation,
-                                bool instrumentation_enabled) {
+                                bool instrumentation_enabled,
+                                fml::RefPtr<fml::GpuThreadMerger> gpu_thread_merger) {
   // TODO: The AcquireFrame interface is too broad and must be refactored to get
   // rid of the context and canvas arguments as those seem to be only used for
   // colorspace correctness purposes on the mobile shells.
diff --git a/runtime/flutter_runner/compositor_context.h b/runtime/flutter_runner/compositor_context.h
index d4e2c38..c595afc 100644
--- a/runtime/flutter_runner/compositor_context.h
+++ b/runtime/flutter_runner/compositor_context.h
@@ -43,7 +43,8 @@
       GrContext* gr_context, SkCanvas* canvas,
       flutter::ExternalViewEmbedder* view_embedder,
       const SkMatrix& root_surface_transformation,
-      bool instrumentation_enabled) override;
+      bool instrumentation_enabled,
+      fml::RefPtr<fml::GpuThreadMerger> gpu_thread_merger) override;
 
   FML_DISALLOW_COPY_AND_ASSIGN(CompositorContext);
 };