Replace base::Contains() and find() with one find() call

This CL replaces base::Contains() and find() with one find()
call for the map lookup avoid performing a double map lookup
from |process_mojo_map_| in extensions::RendererStartupHelper.

Bug: 1157200
Change-Id: Ie16f2269fa0ad70d22e81c9f7018a172105b63ef
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2588671
Commit-Queue: Daniel Cheng <dcheng@chromium.org>
Reviewed-by: Reilly Grant <reillyg@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#836713}

extensions/browser/renderer_startup_helper.cc

@@ -318,9 +318,10 @@ RendererStartupHelper::BindNewRendererRemote(
 
 mojom::Renderer* RendererStartupHelper::GetRenderer(
     content::RenderProcessHost* process) {
-  if (!base::Contains(process_mojo_map_, process))
+  auto it = process_mojo_map_.find(process);
+  if (it == process_mojo_map_.end())
     return nullptr;
-  return process_mojo_map_.find(process)->second.get();
+  return it->second.get();
 }
 //////////////////////////////////////////////////////////////////////////////