Fix lowPowerModeEnabled crash on iOS8

webrtc/modules/utility/source/helpers_ios.mm

Index: webrtc/modules/utility/source/helpers_ios.mm
diff --git a/webrtc/modules/utility/source/helpers_ios.mm b/webrtc/modules/utility/source/helpers_ios.mm
index 4b28cee3dc97e0f3afd132d95f121d35b6d27a32..a312f032d13f6bd8460f04b8df904ef1a42dc316 100644
--- a/webrtc/modules/utility/source/helpers_ios.mm
+++ b/webrtc/modules/utility/source/helpers_ios.mm
@@ -170,7 +170,12 @@ int GetProcessorCount() {
 }
 
 bool GetLowPowerModeEnabled() {
-  return [NSProcessInfo processInfo].lowPowerModeEnabled;
+  NSProcessInfo* info = [NSProcessInfo processInfo];
+  // lowPoweredModeEnabled is only available on iOS9+.
+  if ([info respondsToSelector:@selector(lowPoweredModeEnabled)]) {

[henrika_webrtc, 2016/02/26 08:24:24]

Just learning. Is this the way to go to check for method support? On Android, we
usually make a more explicit check by asking for the OS version. Like this one
better.

+    return info.lowPowerModeEnabled;
+  }
+  return false;
 }
 
 }  // namespace ios