[Fuchsia] use scenic ozone platform by default.

Previously headless ozone platform was used on Fuchsia. Switched it to
scenic. content_unittests fail with scenic, so this change also adds
--ozone-platforms=headless flag in the unittests, until this issue
is resolved.

Bug: 829980, 865172
Change-Id: I8a0b282953cf90554dc78ed1575d927b53374c58
Reviewed-on: https://chromium-review.googlesource.com/1142492Reviewed-by: Scott Violet <sky@chromium.org>
Commit-Queue: Sergey Ulanov <sergeyu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#576360}

content/public/test/DEPS

@@ -10,6 +10,7 @@ include_rules = [
   "+services/network",
   "+services/resource_coordinator",
   "+services/service_manager",
+  "+ui/ozone/public",
   "+v8/include/v8.h",
 ]
 

content/public/test/unittest_test_suite.cc

@@ -21,18 +21,28 @@
 #include "ui/gfx/x/x11.h"
 #endif
 
+#if defined(OS_FUCHSIA)
+#include "ui/ozone/public/ozone_switches.h"
+#endif
+
 namespace content {
 
 UnitTestTestSuite::UnitTestTestSuite(base::TestSuite* test_suite)
     : test_suite_(test_suite) {
-  const base::CommandLine* command_line =
-      base::CommandLine::ForCurrentProcess();
+  base::CommandLine* command_line = base::CommandLine::ForCurrentProcess();
   std::string enabled =
       command_line->GetSwitchValueASCII(switches::kEnableFeatures);
   std::string disabled =
       command_line->GetSwitchValueASCII(switches::kDisableFeatures);
   feature_list_.InitFromCommandLine(enabled, disabled);
 
+#if defined(OS_FUCHSIA)
+  // Use headless ozone platform on Fuchsia by default.
+  // TODO(crbug.com/865172): Remove this flag.
+  if (!command_line->HasSwitch(switches::kOzonePlatform))
+    command_line->AppendSwitchASCII(switches::kOzonePlatform, "headless");
+#endif
+
 #if defined(USE_X11)
   XInitThreads();
 #endif

ui/ozone/ozone.gni

@@ -72,12 +72,8 @@ declare_args() {
       ozone_platform = "windows"
       ozone_platform_windows = true
     } else if (is_fuchsia) {
-      # TODO(crbug.com/829980): Uncomment this line to set scenic as default
-      # on fuchsia. Currently this breaks content_unittests on test bots.
-      #
-      # ozone_platform = "scenic"
+      ozone_platform = "scenic"
       ozone_platform_scenic = true
-
       ozone_platform_magma = true
     }
   }