Remove all code for iOS 8 and below.

Bug: webrtc:8455
Change-Id: I59ae663cea3d734090baa21843e84b8e0ad04c59
Reviewed-on: https://webrtc-review.googlesource.com/16080
Commit-Queue: Kári Helgason <kthelgason@webrtc.org>
Reviewed-by: Daniela Jovanoska Petrenko <denicija@webrtc.org>
Reviewed-by: Henrik Andreassson <henrika@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#20977}
diff --git a/sdk/objc/Framework/Classes/Common/UIDevice+RTCDevice.mm b/sdk/objc/Framework/Classes/Common/UIDevice+RTCDevice.mm
index 3120827..b2cfb20 100644
--- a/sdk/objc/Framework/Classes/Common/UIDevice+RTCDevice.mm
+++ b/sdk/objc/Framework/Classes/Common/UIDevice+RTCDevice.mm
@@ -89,10 +89,6 @@
   return [self currentDevice].systemVersion.doubleValue;
 }
 
-+ (BOOL)isIOS9OrLater {
-  return [self currentDeviceSystemVersion] >= 9.0;
-}
-
 + (BOOL)isIOS11OrLater {
   return [self currentDeviceSystemVersion] >= 11.0;
 }
diff --git a/sdk/objc/Framework/Classes/Common/helpers.mm b/sdk/objc/Framework/Classes/Common/helpers.mm
index 4409845..657a4a2 100644
--- a/sdk/objc/Framework/Classes/Common/helpers.mm
+++ b/sdk/objc/Framework/Classes/Common/helpers.mm
@@ -24,12 +24,6 @@
 namespace webrtc {
 namespace ios {
 
-#if defined(WEBRTC_IOS)
-bool isOperatingSystemAtLeastVersion(double version) {
-  return GetSystemVersion() >= version;
-}
-#endif
-
 NSString* NSStringFromStdString(const std::string& stdString) {
   // std::string may contain null termination character so we construct
   // using length.
@@ -74,19 +68,14 @@
   return StdStringFromNSString(osVersion);
 }
 
-double GetSystemVersion() {
-  static dispatch_once_t once_token;
-  static double system_version;
-  dispatch_once(&once_token, ^{
-    system_version = [UIDevice currentDevice].systemVersion.doubleValue;
-  });
-  return system_version;
-}
-
 std::string GetDeviceType() {
   NSString* deviceModel = [[UIDevice currentDevice] model];
   return StdStringFromNSString(deviceModel);
 }
+
+bool GetLowPowerModeEnabled() {
+  return [NSProcessInfo processInfo].lowPowerModeEnabled;
+}
 #endif
 
 std::string GetDeviceName() {
@@ -117,19 +106,6 @@
   return [NSProcessInfo processInfo].processorCount;
 }
 
-#if defined(__IPHONE_9_0) && defined(__IPHONE_OS_VERSION_MAX_ALLOWED) \
-    && __IPHONE_OS_VERSION_MAX_ALLOWED >= __IPHONE_9_0
-bool GetLowPowerModeEnabled() {
-  if (isOperatingSystemAtLeastVersion(9.0)) {
-    // lowPoweredModeEnabled is only available on iOS9+.
-    return [NSProcessInfo processInfo].lowPowerModeEnabled;
-  }
-  RTC_LOG(LS_WARNING) << "webrtc::ios::GetLowPowerModeEnabled() is not "
-                         "supported. Requires at least iOS 9.0";
-  return false;
-}
-#endif
-
 }  // namespace ios
 }  // namespace webrtc