Fix preload scanner logic to consider lazyload only for images

Add adds param for lazyload experiment,
enable-lazy-load-images-metadata-fetch is likely to be false when
launching

TBR=holte@chromium.org

Change-Id: Iaaa9977a8834f0e6c9cee02adbba90cd37d01aca
Bug: 950645
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1707176
Commit-Queue: rajendrant <rajendrant@chromium.org>
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Reviewed-by: Tarun Bansal <tbansal@chromium.org>
Cr-Commit-Position: refs/heads/master@{#679791}

chrome/browser/page_load_metrics/observers/data_saver_site_breakdown_metrics_observer_browsertest.cc

@@ -63,7 +63,8 @@ class DataSaverSiteBreakdownMetricsObserverBrowserTest
   void SetUp() override {
     scoped_feature_list_.InitWithFeaturesAndParameters(
         {{features::kLazyImageLoading,
-          {{"automatic-lazy-load-images-enabled", "true"}}}},
+          {{"automatic-lazy-load-images-enabled", "true"},
+           {"enable-lazy-load-images-metadata-fetch", "true"}}}},
         {});
     InProcessBrowserTest::SetUp();
   }

content/child/runtime_features.cc

@@ -405,7 +405,7 @@ void SetIndividualRuntimeFeatures(
   WebRuntimeFeatures::EnableLazyImageLoadingMetadataFetch(
       base::GetFieldTrialParamByFeatureAsBool(
           features::kLazyImageLoading, "enable-lazy-load-images-metadata-fetch",
-          true));
+          false));
 
   WebRuntimeFeatures::EnablePictureInPicture(
       base::FeatureList::IsEnabled(media::kPictureInPicture));

testing/variations/fieldtrial_testing_config.json

@@ -2818,6 +2818,7 @@
                     "params": {
                         "automatic-lazy-load-frames-enabled": "true",
                         "automatic-lazy-load-images-enabled": "true",
+                        "enable-lazy-load-images-metadata-fetch": "false",
                         "restrict-lazy-load-frames-to-data-saver-only": "true",
                         "restrict-lazy-load-images-to-data-saver-only": "true"
                     },

third_party/blink/renderer/core/html/parser/html_preload_scanner.cc

@@ -299,49 +299,51 @@ class TokenPreloadScanner::StartTagScanner {
         document_parameters.lazyload_policy_enforced) {
       effective_loading_attr_value = LoadingAttrValue::kAuto;
     }
-    bool is_lazy_load_image_enabled = false;
-    switch (effective_loading_attr_value) {
-      case LoadingAttrValue::kEager:
-        is_lazy_load_image_enabled = false;
-        break;
-      case LoadingAttrValue::kLazy:
-        is_lazy_load_image_enabled =
-            document_parameters.lazy_load_image_setting !=
-            LocalFrame::LazyLoadImageSetting::kDisabled;
-        break;
-      case LoadingAttrValue::kAuto:
-        if ((width_attr_dimension_type_ ==
-                 HTMLImageElement::LazyLoadDimensionType::kAbsoluteSmall &&
-             height_attr_dimension_type_ ==
-                 HTMLImageElement::LazyLoadDimensionType::kAbsoluteSmall) ||
-            inline_style_dimensions_type_ ==
-                HTMLImageElement::LazyLoadDimensionType::kAbsoluteSmall) {
+    if (type == ResourceType::kImage) {
+      bool is_lazy_load_image_enabled = false;
+      switch (effective_loading_attr_value) {
+        case LoadingAttrValue::kEager:
           is_lazy_load_image_enabled = false;
-        } else {
+          break;
+        case LoadingAttrValue::kLazy:
           is_lazy_load_image_enabled =
-              document_parameters.lazy_load_image_setting ==
-              LocalFrame::LazyLoadImageSetting::kEnabledAutomatic;
-        }
-        break;
-    }
-    // Do not preload if lazyload is possible but metadata fetch is disabled.
-    if (is_lazy_load_image_enabled &&
-        !RuntimeEnabledFeatures::LazyImageLoadingMetadataFetchEnabled()) {
-      return nullptr;
-    }
-    // LazyLoad: Do not preload if absolute dimensions are mentioned in width
-    // and height attributes or in the inline style, and the dimensions are not
-    // small enough.
-    if (is_lazy_load_image_enabled &&
-        ((width_attr_dimension_type_ ==
-              HTMLImageElement::LazyLoadDimensionType::kAbsoluteNotSmall &&
-          height_attr_dimension_type_ ==
-              HTMLImageElement::LazyLoadDimensionType::kAbsoluteNotSmall) ||
-         inline_style_dimensions_type_ ==
-             HTMLImageElement::LazyLoadDimensionType::kAbsoluteNotSmall)) {
-      return nullptr;
+              document_parameters.lazy_load_image_setting !=
+              LocalFrame::LazyLoadImageSetting::kDisabled;
+          break;
+        case LoadingAttrValue::kAuto:
+          if ((width_attr_dimension_type_ ==
+                   HTMLImageElement::LazyLoadDimensionType::kAbsoluteSmall &&
+               height_attr_dimension_type_ ==
+                   HTMLImageElement::LazyLoadDimensionType::kAbsoluteSmall) ||
+              inline_style_dimensions_type_ ==
+                  HTMLImageElement::LazyLoadDimensionType::kAbsoluteSmall) {
+            is_lazy_load_image_enabled = false;
+          } else {
+            is_lazy_load_image_enabled =
+                document_parameters.lazy_load_image_setting ==
+                LocalFrame::LazyLoadImageSetting::kEnabledAutomatic;
+          }
+          break;
+      }
+      // Do not preload if lazyload is possible but metadata fetch is disabled.
+      if (is_lazy_load_image_enabled &&
+          !RuntimeEnabledFeatures::LazyImageLoadingMetadataFetchEnabled()) {
+        return nullptr;
+      }
+      // LazyLoad: Do not preload if absolute dimensions are mentioned in width
+      // and height attributes or in the inline style, and the dimensions are
+      // not small enough.
+      if (is_lazy_load_image_enabled &&
+          ((width_attr_dimension_type_ ==
+                HTMLImageElement::LazyLoadDimensionType::kAbsoluteNotSmall &&
+            height_attr_dimension_type_ ==
+                HTMLImageElement::LazyLoadDimensionType::kAbsoluteNotSmall) ||
+           inline_style_dimensions_type_ ==
+               HTMLImageElement::LazyLoadDimensionType::kAbsoluteNotSmall)) {
+        return nullptr;
+      }
+      request->SetIsLazyLoadImageEnabled(is_lazy_load_image_enabled);
     }
-    request->SetIsLazyLoadImageEnabled(is_lazy_load_image_enabled);
 
     request->SetIntegrityMetadata(integrity_metadata_);