Created the dialog offering the user to merge their account data or keep it

chrome/android/java/src/org/chromium/chrome/browser/firstrun/FirstRunSignInProcessor.java

Index: chrome/android/java/src/org/chromium/chrome/browser/firstrun/FirstRunSignInProcessor.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/firstrun/FirstRunSignInProcessor.java b/chrome/android/java/src/org/chromium/chrome/browser/firstrun/FirstRunSignInProcessor.java
index 16c2cc6be1f5dad0e41c810719ca23c186e962b1..0dc7cd6ac7fec0bfe5781427b330e27e57136197 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/firstrun/FirstRunSignInProcessor.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/firstrun/FirstRunSignInProcessor.java
@@ -84,7 +84,7 @@ public final class FirstRunSignInProcessor {
 
         final boolean setUpSync = getFirstRunFlowSignInSetupSync(activity);
         RecordUserAction.record("Signin_Signin_FromStartPage");
-        signinManager.signIn(accountName, activity, new SignInCallback() {
+        signinManager.signIn(accountName, null, new SignInCallback() {

[gogerald1, 2016/02/22 23:32:19]

SigninManager depends on |activity| to distinguish interactive and forced sign
in, you may need to figure out how to do it right now.

[PEConn, 2016/02/23 15:01:53]

For the code to get to this point, the user has already gone through the
AccountSigninView, so has already been presented with the dialog asking if they
want to merge their data or keep it separate (and if they chose to keep it
separate, their old data has already been cleared).

[gogerald1, 2016/02/23 16:57:19]

Yes, but there are some other things need to be done for interactive sign in
only in SigninManager, like managed account confirmation (policy check),
histograms and user actions recording. You probably need to move them out from
SigninManager to somewhere else. In addition, remove |activity| if it is always
supposed to be null and related code in SigninManager. Clean
ConfirmAccountChangeFragment related code in SigninManager as well

[PEConn, 2016/02/24 11:37:51]

Good point. I'll change this back to |activity|.

It may be worth splitting out the ConfirmAccountChangeFragment, but it's not in
the scope of this CL.

[gogerald1, 2016/02/26 01:02:03]

This is not the only place needs to be taken care of (all interactive sign in).

             @Override
             public void onSignInComplete() {
                 // Show sync settings if user pressed the "Settings" button.