Enables DeferAllScript previews by default for Android in M80+

Bug: 960961
Change-Id: I0d1003f4723d7482860e35cae50aeea8c77b835b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1894322
Commit-Queue: Doug Arnett <dougarnett@chromium.org>
Reviewed-by: Ilya Sherman <isherman@chromium.org>
Reviewed-by: Tarun Bansal <tbansal@chromium.org>
Cr-Commit-Position: refs/heads/master@{#712693}

chrome/browser/previews/previews_content_util_unittest.cc

@@ -166,14 +166,14 @@ TEST_F(PreviewsContentUtilTest,
        DetermineAllowedClientPreviewsStateDataSaverDisabled) {
   base::test::ScopedFeatureList scoped_feature_list;
   scoped_feature_list.InitFromCommandLine(
-      "Previews,ResourceLoadingHints,NoScriptPreviews",
+      "Previews,DeferAllScript,ResourceLoadingHints,NoScriptPreviews",
       {} /* disable_features */);
   PreviewsUserData user_data(1);
   bool is_reload = false;
   bool previews_triggering_logic_already_ran = false;
   bool is_data_saver_user = true;
-  EXPECT_EQ(content::OFFLINE_PAGE_ON | content::RESOURCE_LOADING_HINTS_ON |
-                content::NOSCRIPT_ON,
+  EXPECT_EQ(content::OFFLINE_PAGE_ON | content::DEFER_ALL_SCRIPT_ON |
+                content::RESOURCE_LOADING_HINTS_ON | content::NOSCRIPT_ON,
             previews::CallDetermineAllowedClientPreviewsState(
                 &user_data, GURL("http://www.google.com"), is_reload,
                 previews_triggering_logic_already_ran, is_data_saver_user,
@@ -190,7 +190,7 @@ TEST_F(PreviewsContentUtilTest,
        DetermineAllowedClientPreviewsStateOfflineAndRedirects) {
   base::test::ScopedFeatureList scoped_feature_list;
   scoped_feature_list.InitFromCommandLine(
-      "Previews", "ResourceLoadingHints,NoScriptPreviews");
+      "Previews", "DeferAllScript,ResourceLoadingHints,NoScriptPreviews");
   PreviewsUserData user_data(1);
   bool is_reload = false;
   bool previews_triggering_logic_already_ran = false;

components/previews/content/previews_decider_impl_unittest.cc

@@ -1536,7 +1536,7 @@ TEST_F(PreviewsDeciderImplTest, ResourceLoadingHintsCommitTimeWhitelistCheck) {
   }
 }
 
-TEST_F(PreviewsDeciderImplTest, DeferAllScriptNotAllowedByDefault) {
+TEST_F(PreviewsDeciderImplTest, DeferAllScriptDefaultBehavior) {
   base::test::ScopedFeatureList scoped_feature_list;
   scoped_feature_list.InitWithFeatures(
       {features::kPreviews, optimization_guide::features::kOptimizationHints},
@@ -1549,8 +1549,15 @@ TEST_F(PreviewsDeciderImplTest, DeferAllScriptNotAllowedByDefault) {
   content::MockNavigationHandle navigation_handle;
   navigation_handle.set_url(GURL("https://www.google.com"));
 
-  EXPECT_FALSE(previews_decider_impl()->ShouldAllowPreviewAtNavigationStart(
-      &user_data, &navigation_handle, false, PreviewsType::DEFER_ALL_SCRIPT));
+#if defined(OS_ANDROID)
+  bool expected = true;
+#else   // !defined(OS_ANDROID)
+  bool expected = false;
+#endif  // defined(OS_ANDROID)
+  EXPECT_EQ(expected,
+            previews_decider_impl()->ShouldAllowPreviewAtNavigationStart(
+                &user_data, &navigation_handle, false,
+                PreviewsType::DEFER_ALL_SCRIPT));
 }
 
 TEST_F(PreviewsDeciderImplTest,

components/previews/core/previews_features.cc

@@ -92,7 +92,11 @@ const base::Feature kExcludedMediaSuffixes{"PreviewsExcludedMediaSuffixes",
 // Support for enabling DeferAllScript previews which includes a base feature
 // and a UserConsistent-specific experiment feature.
 const base::FeatureState kDeferAllScriptDefaultFeatureState =
+#if defined(OS_ANDROID)
+    base::FEATURE_ENABLED_BY_DEFAULT;
+#else   // !defined(OS_ANDROID)
     base::FEATURE_DISABLED_BY_DEFAULT;
+#endif  // defined(OS_ANDROID)
 const base::Feature kDeferAllScriptPreviews{"DeferAllScript",
                                             kDeferAllScriptDefaultFeatureState};
 const base::Feature kDeferAllScriptPreviewsUserConsistentStudy{

testing/variations/fieldtrial_testing_config.json

@@ -1885,21 +1885,6 @@
             ]
         }
     ],
-    "DeferAllScript": [
-        {
-            "platforms": [
-                "android"
-            ],
-            "experiments": [
-                {
-                    "name": "DeferAllScriptPreviews_Enabled_20190814",
-                    "enable_features": [
-                        "DeferAllScript"
-                    ]
-                }
-            ]
-        }
-    ],
     "DialMediaRouteProvider": [
         {
             "platforms": [