[aw] Add flag to run renderer in little cores

Bug: 1111789
Change-Id: I53dec0cac2c6a28ea70aa7ee215cd4c1325ef054
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2421653
Commit-Queue: Laís Minchillo <laisminchillo@chromium.org>
Auto-Submit: Laís Minchillo <laisminchillo@chromium.org>
Reviewed-by: Eric Seckler <eseckler@chromium.org>
Reviewed-by: Richard Coles <torne@chromium.org>
Cr-Commit-Position: refs/heads/master@{#811696}

android_webview/browser/aw_content_browser_client.cc

@@ -420,6 +420,11 @@ void AwContentBrowserClient::AppendExtraCommandLineSwitches(
             ::switches::kEnableCrashReporterForTesting)) {
       command_line->AppendSwitch(::switches::kEnableCrashReporterForTesting);
     }
+    // Pass WebView's force little cores flag to renderer process.
+    if (base::CommandLine::ForCurrentProcess()->HasSwitch(
+            ::switches::kWebViewForceLittleCores)) {
+      command_line->AppendSwitch(::switches::kWebViewForceLittleCores);
+    }
   }
 }
 

android_webview/common/aw_switches.cc

@@ -49,4 +49,7 @@ const char kFinchSeedMinDownloadPeriod[] = "finch-seed-min-download-period";
 // variations seed.
 const char kFinchSeedMinUpdatePeriod[] = "finch-seed-min-update-period";
 
+// Force WebView renderer to run in little cores
+const char kWebViewForceLittleCores[] = "webview-force-little-cores";
+
 }  // namespace switches

android_webview/common/aw_switches.h

@@ -18,6 +18,7 @@ extern const char kFinchSeedExpirationAge[];
 extern const char kFinchSeedIgnorePendingDownload[];
 extern const char kFinchSeedMinDownloadPeriod[];
 extern const char kFinchSeedMinUpdatePeriod[];
+extern const char kWebViewForceLittleCores[];
 
 }  // namespace switches
 

android_webview/java/src/org/chromium/android_webview/common/ProductionSupportedFlagList.java

@@ -88,5 +88,7 @@ public final class ProductionSupportedFlagList {
                             + "Elements v0, and HTML Imports)."),
             Flag.baseFeature(AwFeatures.WEBVIEW_DISPLAY_CUTOUT,
                     "Enables display cutout (notch) support in WebView for Android P and above."),
+            Flag.commandLine(AwSwitches.WEBVIEW_FORCE_LITTLE_CORES,
+                    "Forces WebView to do rendering work in little cores"),
     };
 }

android_webview/lib/aw_main_delegate.cc

@@ -28,6 +28,7 @@
 #include "base/check_op.h"
 #include "base/command_line.h"
 #include "base/cpu.h"
+#include "base/cpu_affinity_posix.h"
 #include "base/i18n/icu_util.h"
 #include "base/i18n/rtl.h"
 #include "base/posix/global_descriptors.h"
@@ -298,6 +299,10 @@ void AwMainDelegate::PreSandboxStartup() {
 
   if (process_type == switches::kRendererProcess) {
     InitResourceBundleRendererSide();
+    if (command_line.HasSwitch(switches::kWebViewForceLittleCores)) {
+      base::SetProcessCpuAffinityMode(base::GetCurrentProcessHandle(),
+                                      base::CpuAffinityMode::kLittleCoresOnly);
+    }
   }
 
   EnableCrashReporter(process_type);