LazyLoad: Add feature and flags for lazyloading image

Subsequent CLs will implement the feature.

Bug: 846170
Change-Id: Idf8e6352d3c0573a0cf014cc89b2f63251e26607
Reviewed-on: https://chromium-review.googlesource.com/1157143
Commit-Queue: rajendrant <rajendrant@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Cr-Commit-Position: refs/heads/master@{#582216}

chrome/browser/about_flags.cc

@@ -3937,6 +3937,11 @@ const FeatureEntry kFeatureEntries[] = {
      flag_descriptions::kEnableLayoutNGDescription, kOsAll,
      FEATURE_VALUE_TYPE(blink::features::kLayoutNG)},
 
+    {"enable-lazy-image-loading",
+     flag_descriptions::kEnableLazyImageLoadingName,
+     flag_descriptions::kEnableLazyImageLoadingDescription, kOsAll,
+     FEATURE_VALUE_TYPE(features::kLazyImageLoading)},
+
     {"enable-lazy-frame-loading",
      flag_descriptions::kEnableLazyFrameLoadingName,
      flag_descriptions::kEnableLazyFrameLoadingDescription, kOsAll,

chrome/browser/flag_descriptions.cc

@@ -570,6 +570,10 @@ const char kEnableLazyFrameLoadingDescription[] =
     "Defers the loading of certain cross-origin frames until the page is "
     "scrolled down near them.";
 
+const char kEnableLazyImageLoadingName[] = "Enable lazy image loading";
+const char kEnableLazyImageLoadingDescription[] =
+    "Defers the loading of images until the page is scrolled down near them.";
+
 const char kEnableMacMaterialDesignDownloadShelfName[] =
     "Enable Material Design download shelf";
 

chrome/browser/flag_descriptions.h

@@ -372,6 +372,9 @@ extern const char kEnableLayoutNGDescription[];
 extern const char kEnableLazyFrameLoadingName[];
 extern const char kEnableLazyFrameLoadingDescription[];
 
+extern const char kEnableLazyImageLoadingName[];
+extern const char kEnableLazyImageLoadingDescription[];
+
 extern const char kEnableMacMaterialDesignDownloadShelfName[];
 extern const char kEnableMacMaterialDesignDownloadShelfDescription[];
 

content/child/runtime_features.cc

@@ -415,6 +415,10 @@ void SetRuntimeFeaturesDefaultsAndUpdateFromArgs(
     WebRuntimeFeatures::EnableLazyFrameLoading(true);
   if (base::FeatureList::IsEnabled(features::kLazyFrameVisibleLoadTimeMetrics))
     WebRuntimeFeatures::EnableLazyFrameVisibleLoadTimeMetrics(true);
+  if (base::FeatureList::IsEnabled(features::kLazyImageLoading))
+    WebRuntimeFeatures::EnableLazyImageLoading(true);
+  if (base::FeatureList::IsEnabled(features::kLazyImageVisibleLoadTimeMetrics))
+    WebRuntimeFeatures::EnableLazyImageVisibleLoadTimeMetrics(true);
 
   WebRuntimeFeatures::EnableV8ContextSnapshot(
       base::FeatureList::IsEnabled(features::kV8ContextSnapshot));

content/public/common/content_features.cc

@@ -208,6 +208,10 @@ const base::Feature kLazyFrameLoading{"LazyFrameLoading",
                                       base::FEATURE_DISABLED_BY_DEFAULT};
 const base::Feature kLazyFrameVisibleLoadTimeMetrics{
     "LazyFrameVisibleLoadTimeMetrics", base::FEATURE_DISABLED_BY_DEFAULT};
+const base::Feature kLazyImageLoading{"LazyImageLoading",
+                                      base::FEATURE_DISABLED_BY_DEFAULT};
+const base::Feature kLazyImageVisibleLoadTimeMetrics{
+    "LazyImageVisibleLoadTimeMetrics", base::FEATURE_DISABLED_BY_DEFAULT};
 
 // Enable lazy initialization of the media controls.
 const base::Feature kLazyInitializeMediaControls{

content/public/common/content_features.h

@@ -57,6 +57,8 @@ CONTENT_EXPORT extern const base::Feature kKeyboardLockAPI;
 CONTENT_EXPORT extern const base::Feature kLayeredAPI;
 CONTENT_EXPORT extern const base::Feature kLazyFrameLoading;
 CONTENT_EXPORT extern const base::Feature kLazyFrameVisibleLoadTimeMetrics;
+CONTENT_EXPORT extern const base::Feature kLazyImageLoading;
+CONTENT_EXPORT extern const base::Feature kLazyImageVisibleLoadTimeMetrics;
 CONTENT_EXPORT extern const base::Feature kLazyInitializeMediaControls;
 CONTENT_EXPORT extern const base::Feature kLazyParseCSS;
 CONTENT_EXPORT extern const base::Feature kLowPriorityIframes;

third_party/blink/public/platform/web_runtime_features.h

@@ -99,6 +99,8 @@ class WebRuntimeFeatures {
   BLINK_PLATFORM_EXPORT static void EnableLayoutNG(bool);
   BLINK_PLATFORM_EXPORT static void EnableLazyFrameLoading(bool);
   BLINK_PLATFORM_EXPORT static void EnableLazyFrameVisibleLoadTimeMetrics(bool);
+  BLINK_PLATFORM_EXPORT static void EnableLazyImageLoading(bool);
+  BLINK_PLATFORM_EXPORT static void EnableLazyImageVisibleLoadTimeMetrics(bool);
   BLINK_PLATFORM_EXPORT static void EnableLazyParseCSS(bool);
   BLINK_PLATFORM_EXPORT static void EnableMediaCapture(bool);
   BLINK_PLATFORM_EXPORT static void EnableMediaSession(bool);

third_party/blink/renderer/platform/exported/web_runtime_features.cc

@@ -200,6 +200,14 @@ void WebRuntimeFeatures::EnableLazyFrameVisibleLoadTimeMetrics(bool enable) {
   RuntimeEnabledFeatures::SetLazyFrameVisibleLoadTimeMetricsEnabled(enable);
 }
 
+void WebRuntimeFeatures::EnableLazyImageLoading(bool enable) {
+  RuntimeEnabledFeatures::SetLazyImageLoadingEnabled(enable);
+}
+
+void WebRuntimeFeatures::EnableLazyImageVisibleLoadTimeMetrics(bool enable) {
+  RuntimeEnabledFeatures::SetLazyImageVisibleLoadTimeMetricsEnabled(enable);
+}
+
 void WebRuntimeFeatures::EnableLazyParseCSS(bool enable) {
   RuntimeEnabledFeatures::SetLazyParseCSSEnabled(enable);
 }

third_party/blink/renderer/platform/runtime_enabled_features.json5

@@ -630,6 +630,12 @@
     {
       name: "LazyFrameVisibleLoadTimeMetrics",
     },
+    {
+      name: "LazyImageLoading",
+    },
+    {
+      name: "LazyImageVisibleLoadTimeMetrics",
+    },
     {
       name: "LazyInitializeMediaControls",
       // This is enabled by features::kLazyInitializeMediaControls.

tools/metrics/histograms/enums.xml

@@ -28152,6 +28152,7 @@ from previous Chrome versions.
   <int value="-1126217973" label="IdleTimeSpellChecking:disabled"/>
   <int value="-1125840399" label="ViewsBrowserWindows:enabled"/>
   <int value="-1125133283" label="disable-threaded-scrolling"/>
+  <int value="-1122853453" label="LazyImageLoading:enabled"/>
   <int value="-1121931029" label="DownloadsForeground:enabled"/>
   <int value="-1119700637" label="ui-disable-partial-swap"/>
   <int value="-1112782121" label="AndroidSigninPromos:disabled"/>
@@ -28428,6 +28429,7 @@ from previous Chrome versions.
   <int value="-536230323" label="SingleClickAutofill:disabled"/>
   <int value="-535662704" label="BundledConnectionHelp:enabled"/>
   <int value="-535208779" label="enable-native-cups"/>
+  <int value="-534221085" label="LazyImageLoading:disabled"/>
   <int value="-533552313"
       label="AutofillUpstreamEditableCardholderName:enabled"/>
   <int value="-531810064" label="saveas-menu-label"/>