Update IMA and Play Services

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=198536438

constants.gradle

@@ -25,7 +25,7 @@ project.ext {
     buildToolsVersion = '27.0.3'
     testSupportLibraryVersion = '0.5'
     supportLibraryVersion = '27.0.0'
-    playServicesLibraryVersion = '12.0.0'
+    playServicesLibraryVersion = '15.0.1'
     dexmakerVersion = '1.2'
     mockitoVersion = '1.9.5'
     junitVersion = '4.12'

extensions/cast/build.gradle

@@ -30,9 +30,10 @@ dependencies {
     // com.android.support:support-v4, com.android.support:appcompat-v7 and
     // com.android.support:mediarouter-v7 to be used. Else older versions are
     // used, for example:
-    // com.google.android.gms:play-services-cast-framework:12.0.0
-    // |-- com.google.android.gms:play-services-basement:12.0.0
-    //   |-- com.android.support:support-v4:26.1.0
+    // com.google.android.gms:play-services-cast-framework:15.0.1
+    // |-- com.google.android.gms:play-services-base:15.0.1
+    //   |-- com.google.android.gms:play-services-basement:15.0.1
+    //     |-- com.android.support:support-v4:26.1.0
     api 'com.android.support:support-v4:' + supportLibraryVersion
     api 'com.android.support:appcompat-v7:' + supportLibraryVersion
     api 'com.android.support:mediarouter-v7:' + supportLibraryVersion

extensions/ima/build.gradle

@@ -27,14 +27,14 @@ android {
 
 dependencies {
     // This dependency is necessary to force the supportLibraryVersion of
-    // com.android.support:support-v4 to be used. Else an older version (25.2.0)
-    // is included via:
-    // com.google.android.gms:play-services-ads:12.0.0
-    // |-- com.google.android.gms:play-services-ads-lite:12.0.0
-    //   |-- com.google.android.gms:play-services-basement:12.0.0
+    // com.android.support:support-v4 to be used. Else an older version is
+    // included via:
+    // com.google.android.gms:play-services-ads:15.0.1
+    // |-- com.google.android.gms:play-services-ads-identifier:15.0.1
+    //   |-- com.google.android.gms:play-services-basement:15.0.1
     //     |-- com.android.support:support-v4:26.1.0
     api 'com.android.support:support-v4:' + supportLibraryVersion
-    api 'com.google.ads.interactivemedia.v3:interactivemedia:3.8.5'
+    api 'com.google.ads.interactivemedia.v3:interactivemedia:3.8.7'
     implementation project(modulePrefix + 'library-core')
     implementation 'com.google.android.gms:play-services-ads:' + playServicesLibraryVersion
 }