[Flags] Add --enable-webassembly-baseline to about:flags

This allows to enable Liftoff, the baseline compiler for WebAssembly.

R=hablich@chromium.org, titzer@chromium.org, jochen@chromium.org

Bug: 787421
Change-Id: Ie6877e72db50f4daa55413fabd70aca74ccf0e6c
Reviewed-on: https://chromium-review.googlesource.com/1032330Reviewed-by: Michael Hablich <hablich@chromium.org>
Reviewed-by: Jochen Eisinger <jochen@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#554372}

chrome/browser/about_flags.cc

@@ -1404,6 +1404,9 @@ const FeatureEntry kFeatureEntries[] = {
      flag_descriptions::kEnableWasmStreamingName,
      flag_descriptions::kEnableWasmStreamingDescription, kOsAll,
      FEATURE_VALUE_TYPE(features::kWebAssemblyStreaming)},
+    {"enable-webassembly-baseline", flag_descriptions::kEnableWasmBaselineName,
+     flag_descriptions::kEnableWasmBaselineDescription, kOsAll,
+     FEATURE_VALUE_TYPE(features::kWebAssemblyBaseline)},
     {"shared-array-buffer", flag_descriptions::kEnableSharedArrayBufferName,
      flag_descriptions::kEnableSharedArrayBufferDescription, kOsAll,
      FEATURE_VALUE_TYPE(features::kSharedArrayBuffer)},

chrome/browser/flag_descriptions.cc

@@ -668,6 +668,10 @@ const char kEnableWasmStreamingName[] =
 const char kEnableWasmStreamingDescription[] =
     "WebAssembly.{compile|instantiate} taking a Response as parameter.";
 
+const char kEnableWasmBaselineName[] = "WebAssembly baseline compiler";
+const char kEnableWasmBaselineDescription[] =
+    "Enables WebAssembly baseline compilation and tier up.";
+
 const char kExpensiveBackgroundTimerThrottlingName[] =
     "Throttle expensive background timers";
 const char kExpensiveBackgroundTimerThrottlingDescription[] =

chrome/browser/flag_descriptions.h

@@ -428,6 +428,9 @@ extern const char kEnableZeroSuggestRedirectToChromeDescription[];
 extern const char kEnableWasmStreamingName[];
 extern const char kEnableWasmStreamingDescription[];
 
+extern const char kEnableWasmBaselineName[];
+extern const char kEnableWasmBaselineDescription[];
+
 extern const char kExpensiveBackgroundTimerThrottlingName[];
 extern const char kExpensiveBackgroundTimerThrottlingDescription[];
 

content/public/common/content_features.cc

@@ -456,7 +456,11 @@ const base::Feature kWebAssembly{"WebAssembly",
 const base::Feature kWebAssemblyStreaming{"WebAssemblyStreaming",
                                           base::FEATURE_ENABLED_BY_DEFAULT};
 
-// Enable WebAssembly streamed compilation.
+// Enable WebAssembly baseline compilation and tier up.
+const base::Feature kWebAssemblyBaseline{"WebAssemblyBaseline",
+                                         base::FEATURE_DISABLED_BY_DEFAULT};
+
+// Enable WebAssembly trap handler.
 const base::Feature kWebAssemblyTrapHandler{"WebAssemblyTrapHandler",
                                             base::FEATURE_DISABLED_BY_DEFAULT};
 

content/public/common/content_features.h

@@ -108,6 +108,7 @@ CONTENT_EXPORT extern const base::Feature kV8VmFuture;
 CONTENT_EXPORT extern const base::Feature kVrWebInputEditing;
 CONTENT_EXPORT extern const base::Feature kWebAssembly;
 CONTENT_EXPORT extern const base::Feature kWebAssemblyStreaming;
+CONTENT_EXPORT extern const base::Feature kWebAssemblyBaseline;
 CONTENT_EXPORT extern const base::Feature kWebAssemblyTrapHandler;
 CONTENT_EXPORT extern const base::Feature kWebAuth;
 CONTENT_EXPORT extern const base::Feature kWebAuthBle;

content/renderer/render_process_impl.cc

@@ -143,6 +143,10 @@ RenderProcessImpl::RenderProcessImpl(
 
   SetV8FlagIfFeature(features::kV8VmFuture, "--future");
   SetV8FlagIfNotFeature(features::kV8VmFuture, "--no-future");
+
+  SetV8FlagIfFeature(features::kWebAssemblyBaseline, "--wasm-tier-up");
+  SetV8FlagIfNotFeature(features::kWebAssemblyBaseline, "--no-wasm-tier-up");
+
   SetV8FlagIfFeature(features::kSharedArrayBuffer,
                      "--harmony-sharedarraybuffer");
   SetV8FlagIfNotFeature(features::kSharedArrayBuffer,

tools/metrics/histograms/enums.xml

@@ -27200,6 +27200,7 @@ from previous Chrome versions.
       label="enable-manual-fallback-for-password-saving:disabled"/>
   <int value="241187301" label="BrowserTouchBar:disabled"/>
   <int value="244697230" label="enable-theme-color-in-tabbed-mode"/>
+  <int value="250855010" label="WebAssemblyBaseline:disabled"/>
   <int value="255375615" label="stop-non-timers-in-background:enabled"/>
   <int value="259021228" label="OffMainThreadFetch:disabled"/>
   <int value="262382944" label="GuestViewCrossProcessFrames:disabled"/>
@@ -27605,6 +27606,7 @@ from previous Chrome versions.
   <int value="1179936481" label="enable-android-pay-integration-v1"/>
   <int value="1180722846" label="OculusVR:disabled"/>
   <int value="1181056275" label="enable-cloud-backup"/>
+  <int value="1183260592" label="WebAssemblyBaseline:enabled"/>
   <int value="1183431946" label="v8-cache-options"/>
   <int value="1185424279" label="enable-media-router"/>
   <int value="1190035852" label="MediaRemoting:enabled"/>