LazyLoad: Add option to enable lazy frame loading in about:flags

Bug: 635105
Change-Id: Ic1d61399cf3b1f5aafeed64238c25250849d43a4
Reviewed-on: https://chromium-review.googlesource.com/1011386Reviewed-by: Ryan Sturm <ryansturm@chromium.org>
Commit-Queue: Scott Little <sclittle@chromium.org>
Cr-Commit-Position: refs/heads/master@{#550491}

chrome/browser/about_flags.cc

@@ -3845,6 +3845,11 @@ const FeatureEntry kFeatureEntries[] = {
      FEATURE_VALUE_TYPE(features::kIncreaseInputAudioBufferSize)},
 #endif  // OS_WIN
 
+    {"enable-lazy-frame-loading",
+     flag_descriptions::kEnableLazyFrameLoadingName,
+     flag_descriptions::kEnableLazyFrameLoadingDescription, kOsAll,
+     FEATURE_VALUE_TYPE(features::kLazyFrameLoading)}
+
     // NOTE: Adding a new flag requires adding a corresponding entry to enum
     // "LoginCustomFlags" in tools/metrics/histograms/enums.xml. See "Flag
     // Histograms" in tools/metrics/histograms/README.md (run the

chrome/browser/flag_descriptions.cc

@@ -418,6 +418,11 @@ const char kEnableHttpFormWarningDescription[] =
     "Attaches a warning UI to any password or credit card fields detected when "
     "the top-level page is not HTTPS";
 
+const char kEnableLazyFrameLoadingName[] = "Enable lazy frame loading";
+const char kEnableLazyFrameLoadingDescription[] =
+    "Defers the loading of certain cross-origin frames until the page is "
+    "scrolled down near them.";
+
 const char kEnableMacMaterialDesignDownloadShelfName[] =
     "Enable Material Design download shelf";
 

chrome/browser/flag_descriptions.h

@@ -291,6 +291,9 @@ extern const char kEnableHeapProfilingTaskProfiler[];
 extern const char kEnableHttpFormWarningName[];
 extern const char kEnableHttpFormWarningDescription[];
 
+extern const char kEnableLazyFrameLoadingName[];
+extern const char kEnableLazyFrameLoadingDescription[];
+
 extern const char kEnableMacMaterialDesignDownloadShelfName[];
 extern const char kEnableMacMaterialDesignDownloadShelfDescription[];
 

tools/metrics/histograms/enums.xml

@@ -27034,6 +27034,7 @@ from previous Chrome versions.
   <int value="388996324" label="CustomContextMenu:disabled"/>
   <int value="393704200" label="account-consistency"/>
   <int value="398903399" label="GenericSensorExtraClasses:disabled"/>
+  <int value="400272381" label="LazyFrameLoading:disabled"/>
   <int value="400322063" label="ash-disable-screen-orientation-lock"/>
   <int value="401983950" label="enable-spdy4"/>
   <int value="402143634" label="enable-search-button-in-omnibox-always"/>
@@ -27459,6 +27460,7 @@ from previous Chrome versions.
   <int value="1371907429" label="enable-wallet-card-import"/>
   <int value="1372680885" label="enable-mtp-write-support"/>
   <int value="1373777956" label="disable-threaded-gpu-rasterization"/>
+  <int value="1375165388" label="LazyFrameLoading:enabled"/>
   <int value="1376437124" label="show-cert-link"/>
   <int value="1377056573" label="browser-side-navigation:enabled"/>
   <int value="1378310092" label="disable-suggestions-service"/>