Add a prototype today extension behind gn flag

ios/chrome/widget_extension/Info.plist

Index: ios/chrome/widget_extension/Info.plist
diff --git a/ios/chrome/widget_extension/Info.plist b/ios/chrome/widget_extension/Info.plist
new file mode 100644
index 0000000000000000000000000000000000000000..07601a97ab7b306529d2b7d173b042afc3be9ccd
--- /dev/null
+++ b/ios/chrome/widget_extension/Info.plist
@@ -0,0 +1,35 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+	<key>CFBundleDevelopmentRegion</key>
+	<string>en</string>
+	<key>CFBundleDisplayName</key>
+	<string>${CHROMIUM_SHORT_NAME}</string>
+	<key>CFBundleExecutable</key>
+	<string>proto_today_extension</string>
+	<key>CFBundleIdentifier</key>
+	<string>${IOS_BUNDLE_ID_PREFIX}.${TODAY_EXTENSION_BUNDLE_ID}</string>

[sdefresne, 2017/01/18 11:11:35]

I would rename TODAY_EXTENSION_BUNDLE_ID to WIDGET_EXTENSION_BUNDLE_ID here too.

[lody, 2017/01/18 14:56:39]

Done.

+	<key>CFBundleInfoDictionaryVersion</key>
+	<string>6.0</string>
+	<key>CFBundleName</key>
+	<string>proto_today_extension</string>
+	<key>CFBundlePackageType</key>
+	<string>XPC!</string>
+	<key>CFBundleShortVersionString</key>
+	<string>1.0</string>
+	<key>CFBundleSignature</key>
+	<string>????</string>
+	<key>CFBundleVersion</key>
+	<string>1</string>
+	<key>NSExtension</key>
+	<dict>
+		<key>NSExtensionPrincipalClass</key>
+		<string>WidgetViewController</string>
+		<key>NSExtensionPointIdentifier</key>
+		<string>com.apple.widget-extension</string>
+	</dict>
+	<key>KSChannelChromeScheme</key>
+	<string>${CHROME_CHANNEL_SCHEME}</string>
+</dict>
+</plist>