Start using the third_party/custom_tabs_client as support lib source

chrome/android/java/proguard.flags

 # Keep line number information, useful for stack traces.
 -keepattributes SourceFile,LineNumberTable
 
 # Keep the annotations.
 -keep @interface ***
 
 # Disable obfuscation for the following two packages.
 -keepnames class com.google.android.apps.chrome.**,org.chromium.** {
   *;
 }
@@ skipping 136 matching lines @@
 }
 
 # TODO(aurimas): remove this when Google Play Services no longer uses setLatestEventInfo call
 # that was deprecated in Android M. It is save to suppress this according to b/18510449.
 -dontwarn android.app.Notification
 
 # IntentUtils uses reflection to access a method that is hidden until API level 18.
 -dontnote org.chromium.chrome.browser.util.IntentUtils
 
 # Needed to compile ChromeTest.apk
--keep class android.support.customtabs.ICustomTabsCallback** {
+-keep class android.support.customtabs.** {
   *;
 }
 
 # Needed to run ChromeTest.apk
 -keepnames class com.google.android.gms.common.GoogleApiAvailability {
   *;
 }
 
 #-keep public class android.net.http.SslCertificate
 #-keep public class android.webkit.WebVie
 
 #-dontwarn android.webkit.WebView
 -dontwarn android.net.http.SslCertificate
 
 # Needed for assertions in BaseChromiumApplication.
 # TODO(twellington): Remove these two lines when support for detecting a debug
 # build lands (https://codereview.chromium.org/1597273005/).
 -keep class android.support.v7.app.ToolbarActionBar$ToolbarCallbackWrapper {*;}
 -keep class android.support.v7.internal.app.ToolbarActionBar$ToolbarCallbackWrapper {*;}