[Tabs] Replace MDCRaisedButton with contained button themer in TabBar…

…IndicatorTemplateExample. (#3500)

Pivotal story: https://www.pivotaltracker.com/story/show/157105832

Before:
![simulator screen shot - iphone se - 2018-04-25 at 20 14 16](https://user-images.githubusercontent.com/45670/39279219-a8eb18b0-48c5-11e8-8c51-dea08ac819d5.png)

After:
![simulator screen shot - iphone se - 2018-04-25 at 20 15 57](https://user-images.githubusercontent.com/45670/39279225-ac8c4200-48c5-11e8-8475-42db5c2a76ba.png)

components/Tabs/examples/TabBarIndicatorTemplateExample.swift

@@ -46,10 +46,11 @@ class TabBarIndicatorTemplateExample: UIViewController {
     }
   }
 
-  lazy var alignmentButton: MDCRaisedButton = self.makeAlignmentButton()
-  lazy var appearanceButton: MDCRaisedButton = self.makeAppearanceButton()
+  lazy var alignmentButton: MDCButton = self.makeAlignmentButton()
+  lazy var appearanceButton: MDCButton = self.makeAppearanceButton()
   lazy var appBar: MDCAppBar = self.makeAppBar()
   var colorScheme = MDCSemanticColorScheme()
+  var typographyScheme = MDCTypographyScheme()
 
   lazy var tabBar: MDCTabBar = {
     let tabBar = MDCTabBar()

components/Tabs/examples/supplemental/TabBarIndicatorTemplateExampleSupplemental.swift

@@ -17,17 +17,27 @@
 import UIKit
 
 import MaterialComponents.MaterialButtons
+import MaterialComponents.MaterialButtons_ButtonThemer
 
 extension TabBarIndicatorTemplateExample {
 
-  func makeAlignmentButton() -> MDCRaisedButton {
-    let button = MDCRaisedButton()
+  private func themeButton(_ button: MDCButton) {
+    let buttonScheme = MDCButtonScheme()
+    buttonScheme.colorScheme = colorScheme
+    buttonScheme.typographyScheme = typographyScheme
+    MDCContainedButtonThemer.applyScheme(buttonScheme, to: button)
+  }
+
+  func makeAlignmentButton() -> MDCButton {
+    let button = MDCButton()
+    themeButton(button)
     button.setTitle("Change Alignment", for: .normal)
     return button
   }
 
-  func makeAppearanceButton() -> MDCRaisedButton {
-    let button = MDCRaisedButton()
+  func makeAppearanceButton() -> MDCButton {
+    let button = MDCButton()
+    themeButton(button)
     button.setTitle("Change Appearance", for: .normal)
     return button
   }