Make --enable-low-end-device-mode apply in C++ on Android

Currently, Android supports --enable-low-end-device-mode, but requires
that the flag be set/visible to Java. This limits the usefulness, as
we can't apply this flag via C++ in test scenarios. This change
modifies SysInfo::IsLowEndDevice to behave like
SysInfo::AmountOfAvailablePhysicalMemory in its handling of flags:
flags are checked / applied in platform-independent C++ before
forwarding to a platform-specific impl function in the case that
the default behavior was not overridden.

Change-Id: Ic2952ed5d2eb199f4daaa60aa2f1eb6dad87d205
Reviewed-on: https://chromium-review.googlesource.com/959301Reviewed-by: danakj <danakj@chromium.org>
Commit-Queue: Eric Karl <ericrk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#542823}

base/sys_info.cc

@@ -44,6 +44,15 @@ int64_t SysInfo::AmountOfAvailablePhysicalMemory() {
   return AmountOfAvailablePhysicalMemoryImpl();
 }
 
+bool SysInfo::IsLowEndDevice() {
+  if (base::CommandLine::ForCurrentProcess()->HasSwitch(
+          switches::kEnableLowEndDeviceMode)) {
+    return true;
+  }
+
+  return IsLowEndDeviceImpl();
+}
+
 #if !defined(OS_ANDROID)
 
 bool DetectLowEndDevice() {
@@ -62,7 +71,7 @@ static LazyInstance<
   g_lazy_low_end_device = LAZY_INSTANCE_INITIALIZER;
 
 // static
-bool SysInfo::IsLowEndDevice() {
+bool SysInfo::IsLowEndDeviceImpl() {
   return g_lazy_low_end_device.Get().value();
 }
 #endif

base/sys_info.h

@@ -172,6 +172,7 @@ class BASE_EXPORT SysInfo {
 
   static int64_t AmountOfPhysicalMemoryImpl();
   static int64_t AmountOfAvailablePhysicalMemoryImpl();
+  static bool IsLowEndDeviceImpl();
 
 #if defined(OS_LINUX) || defined(OS_ANDROID) || defined(OS_AIX)
   static int64_t AmountOfAvailablePhysicalMemory(

base/sys_info_android.cc

@@ -222,7 +222,7 @@ static base::LazyInstance<
         android::SysUtils::IsLowEndDeviceFromJni> >::Leaky
     g_lazy_low_end_device = LAZY_INSTANCE_INITIALIZER;
 
-bool SysInfo::IsLowEndDevice() {
+bool SysInfo::IsLowEndDeviceImpl() {
   // This code might be used in some environments
   // which might not have a Java environment.
   // Note that we need to call the Java version here.