[ObjC ARC] Converts ios/chrome/browser/ui/material_components:material_components to ARC.

Automatically generated ARCMigrate commit
Notable issues:None
BUG=624363
TEST=None

Review-Url: https://codereview.chromium.org/2888993003
Cr-Commit-Position: refs/heads/master@{#476339}

ios/chrome/browser/ui/material_components/BUILD.gn

@@ -3,6 +3,7 @@
 # found in the LICENSE file.
 
 source_set("material_components") {
+  configs += [ "//build/config/compiler:enable_arc" ]
   sources = [
     "activity_indicator.h",
     "activity_indicator.mm",

ios/chrome/browser/ui/material_components/activity_indicator.mm

@@ -7,6 +7,10 @@
 #import "ios/chrome/browser/ui/colors/MDCPalette+CrAdditions.h"
 #import "ios/third_party/material_components_ios/src/components/Palettes/src/MaterialPalettes.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 NSArray* ActivityIndicatorBrandedCycleColors() {
 #if defined(GOOGLE_CHROME_BUILD)
   return @[

ios/chrome/browser/ui/material_components/app_bar_presenting.h

@@ -15,7 +15,7 @@
 @protocol AppBarPresenting<NSObject>
 
 // The installed app bar, if any.
-@property(nonatomic, readonly) MDCAppBar* appBar;
+@property(nonatomic, readonly, strong) MDCAppBar* appBar;
 
 @end
 

ios/chrome/browser/ui/material_components/utils.mm

@@ -11,6 +11,10 @@
 #import "ios/third_party/material_components_ios/src/components/NavigationBar/src/MaterialNavigationBar.h"
 #import "ios/third_party/material_components_ios/src/components/Palettes/src/MaterialPalettes.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 void ConfigureAppBarWithCardStyle(MDCAppBar* appBar) {
   appBar.headerViewController.headerView.canOverExtend = NO;
   appBar.headerViewController.headerView.shiftBehavior =