Update from https://crrev.com/312398

Involves adding many //testing/test.gni imports, fixing one
SkSurface::NewRenderTarget invocation inside sky, and fixing up
base::Process usage in the shell.

Review URL: https://codereview.chromium.org/862133002

BUILD.gn

diff --git a/BUILD.gn b/BUILD.gn
index 3bffec2..03e90cb 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -2,6 +2,7 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+import("//testing/test.gni")
 import("//url/config.gni")
 
 # Sets the USE_ICU_ALTERNATIVES_ON_ANDROID define based on the build flag.