Add Linux breakpad targets and gtest_main to GN build.

BUILD.gn

 # Copyright (c) 2013 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # This is the root build file for GN. GN will start processing by loading this
 # file, and recursively load all dependencies until all dependencies are either
 # resolved or known not to exist (which will cause the build to fail). So if
 # you add a new build file, there must be some path of dependencies from this
 # file to your new one or GN won't know about it.
 
@@ skipping 83 matching lines @@
     "//ui/resources",
     "//ui/snapshot",
     "//ui/strings",
     "//ui/surface",
     "//url",
     "//v8:v8",
     "//webkit/browser:storage",
     "//webkit/child",
   ]
 
+  if (!is_win) {
+    deps += [ "//breakpad:symupload" ]
+  }
+
   if (is_linux) {
     deps += [
       "//dbus",
       "//third_party/fontconfig",
       "//third_party/freetype2",
     ]
   }
 
   if (is_win) {
     deps += [
@@ skipping 42 matching lines @@
     ]
   }
 
   if (use_ozone) {
     deps += [
       "//ui/events/ozone:events_ozone",
       "//ui/events/ozone:events_ozone_evdev",
     ]
   }
 }