[Android] Add a low-end device mode override flag

The current low-end device optimizations are restricted to devices that meet
certain memory and OS version criteria.  Add a flag that overrides this
detection, simplifying testing and allowing power users to take advantage
of the optimizations.

BUG=320747

Review URL: https://codereview.chromium.org/62833002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@237584 0039d316-1c4b-4281-b951-d872f2087c98

7 files changed, 57 insertions, 6 deletions

diff --git a/base/android/java/src/org/chromium/base/BaseSwitches.java b/base/android/java/src/org/chromium/base/BaseSwitches.java
index 4cda1f5..f9832dd 100644
--- a/base/android/java/src/org/chromium/base/BaseSwitches.java
+++ b/base/android/java/src/org/chromium/base/BaseSwitches.java
@@ -12,6 +12,12 @@ public abstract class BaseSwitches {
     // Block onCreate() of Chrome until a Java debugger is attached.
     public static final String WAIT_FOR_JAVA_DEBUGGER = "wait-for-java-debugger";
 
+    // Overrides low-end device detection, disabling low-end device optimizations.
+    public static final String DISABLE_LOW_END_DEVICE_MODE = "disable-low-end-device-mode";
+
+    // Overrides low-end device detection, enabling low-end device optimizations.
+    public static final String ENABLE_LOW_END_DEVICE_MODE = "enable-low-end-device-mode";
+
     // Prevent instantiation.
     private BaseSwitches() {}
 };
diff --git a/base/android/java/src/org/chromium/base/SysUtils.java b/base/android/java/src/org/chromium/base/SysUtils.java
index 6c2ef5f..61a1a08 100644
--- a/base/android/java/src/org/chromium/base/SysUtils.java
+++ b/base/android/java/src/org/chromium/base/SysUtils.java
@@ -15,6 +15,9 @@ import android.content.Context;
 import android.os.Build;
 import android.util.Log;
 
+import org.chromium.base.BaseSwitches;
+import org.chromium.base.CommandLine;
+
 /**
  * Exposes system related information about the current device.
  */
@@ -98,15 +101,28 @@ public class SysUtils {
      */
     @CalledByNative
     public static boolean isLowEndDevice() {
-        if (Build.VERSION.SDK_INT <= ANDROID_LOW_MEMORY_ANDROID_SDK_THRESHOLD) {
-            return false;
-        }
         if (sLowEndDevice == null) {
-            int ramSizeKB = amountOfPhysicalMemoryKB();
-            sLowEndDevice = (ramSizeKB > 0 &&
-                    ramSizeKB / 1024 < ANDROID_LOW_MEMORY_DEVICE_THRESHOLD_MB);
+            sLowEndDevice = detectLowEndDevice();
         }
 
         return sLowEndDevice.booleanValue();
     }
+
+    private static boolean detectLowEndDevice() {
+        if (CommandLine.isInitialized()) {
+            if (CommandLine.getInstance().hasSwitch(BaseSwitches.ENABLE_LOW_END_DEVICE_MODE)) {
+                return true;
+            }
+            if (CommandLine.getInstance().hasSwitch(BaseSwitches.DISABLE_LOW_END_DEVICE_MODE)) {
+                return false;
+            }
+        }
+
+        if (Build.VERSION.SDK_INT <= ANDROID_LOW_MEMORY_ANDROID_SDK_THRESHOLD) {
+            return false;
+        }
+
+        int ramSizeKB = amountOfPhysicalMemoryKB();
+        return (ramSizeKB > 0 && ramSizeKB / 1024 < ANDROID_LOW_MEMORY_DEVICE_THRESHOLD_MB);
+    }
 }
diff --git a/base/base_switches.cc b/base/base_switches.cc
index c6dce9b..526633c 100644
--- a/base/base_switches.cc
+++ b/base/base_switches.cc
@@ -61,4 +61,12 @@ const char kEnableCrashReporterForTesting[] =
     "enable-crash-reporter-for-testing";
 #endif
 
+#if defined(OS_ANDROID)
+// Overrides low-end device detection, disabling low-end device optimizations.
+const char kDisableLowEndDeviceMode[]       = "disable-low-end-device-mode";
+
+// Overrides low-end device detection, enabling low-end device optimizations.
+const char kEnableLowEndDeviceMode[]        = "enable-low-end-device-mode";
+#endif
+
 }  // namespace switches
diff --git a/base/base_switches.h b/base/base_switches.h
index 33b2b68..b2bf7ab 100644
--- a/base/base_switches.h
+++ b/base/base_switches.h
@@ -27,6 +27,11 @@ extern const char kTraceToConsole[];
 extern const char kEnableCrashReporterForTesting[];
 #endif
 
+#if defined(OS_ANDROID)
+extern const char kDisableLowEndDeviceMode[];
+extern const char kEnableLowEndDeviceMode[];
+#endif
+
 }  // namespace switches
 
 #endif  // BASE_BASE_SWITCHES_H_
diff --git a/chrome/app/generated_resources.grd b/chrome/app/generated_resources.grd
index 42ab546..afc5b6f 100644
--- a/chrome/app/generated_resources.grd
+++ b/chrome/app/generated_resources.grd
@@ -6673,6 +6673,12 @@ Keep your key file in a safe place. You will need it to create new versions of y
         <message name="IDS_FLAGS_DISABLE_CLICK_DELAY_DESCRIPTION" desc="Description of the flag to disable the click delay.">
           Always send click events immediate upon a tap, even when it's part of a double-tap gesture.  This speeds up navigation and other tap actions by 300ms on most pages, but means links and buttons must be avoided when double tapping to zoom.
         </message>
+        <message name="IDS_FLAGS_LOW_END_DEVICE_MODE_DESCRIPTION" desc="Description of the flag to tweak low end device optimizations.">
+          Overrides low end device optimizations.
+        </message>
+        <message name="IDS_FLAGS_LOW_END_DEVICE_MODE_NAME" desc="Name of the flag to tweak low end device optimizations.">
+          Low end device mode.
+        </message>
       </if>
       <message name="IDS_FLAGS_ENABLE_TRANSLATE_NEW_UX_NAME" desc="Name of the flag to enable the new Translate UX.">
         Enable the new Translate UX.
diff --git a/chrome/browser/about_flags.cc b/chrome/browser/about_flags.cc
index b6fb23f..9bab032 100644
--- a/chrome/browser/about_flags.cc
+++ b/chrome/browser/about_flags.cc
@@ -1799,6 +1799,14 @@ const Experiment kExperiments[] = {
     // Java-only switch: CommandLine.DISABLE_CLICK_DELAY
     SINGLE_VALUE_TYPE("disable-click-delay")
   },
+  {
+    "low-end-device-mode",
+     IDS_FLAGS_LOW_END_DEVICE_MODE_NAME,
+     IDS_FLAGS_LOW_END_DEVICE_MODE_DESCRIPTION,
+     kOsAndroid,
+     ENABLE_DISABLE_VALUE_TYPE(switches::kEnableLowEndDeviceMode,
+                               switches::kDisableLowEndDeviceMode)
+  },
 #endif
 #if defined(OS_CHROMEOS)
   {
diff --git a/content/browser/renderer_host/render_process_host_impl.cc b/content/browser/renderer_host/render_process_host_impl.cc
index 455f36d..08e75cf 100644
--- a/content/browser/renderer_host/render_process_host_impl.cc
+++ b/content/browser/renderer_host/render_process_host_impl.cc
@@ -1115,7 +1115,9 @@ void RenderProcessHostImpl::PropagateBrowserCommandLineToRenderer(
 #endif
 #if defined(OS_ANDROID)
     switches::kDisableGestureRequirementForMediaPlayback,
+    switches::kDisableLowEndDeviceMode,
     switches::kDisableWebRTC,
+    switches::kEnableLowEndDeviceMode,
     switches::kEnableSpeechRecognition,
     switches::kHideScrollbars,
     switches::kMediaDrmEnableNonCompositing,