Added a UI for the Interests Prototype.

chrome/android/java/src/org/chromium/chrome/browser/ntp/NewTabPageView.java

Index: chrome/android/java/src/org/chromium/chrome/browser/ntp/NewTabPageView.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/ntp/NewTabPageView.java b/chrome/android/java/src/org/chromium/chrome/browser/ntp/NewTabPageView.java
index d38d11b1b4c5472ed55982bd8b484868724b5039..35d4abd87f1200160a174aef115569d609af0efb 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/ntp/NewTabPageView.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/ntp/NewTabPageView.java
@@ -118,6 +118,9 @@ public class NewTabPageView extends FrameLayout
         /** @return Whether voice search is enabled and the microphone should be shown. */
         boolean isVoiceSearchEnabled();
 
+        /** @return Whether the user is signed in. */
+        boolean isUserSignedIn();
+
         /** @return Whether the document mode opt out promo should be shown. */
         boolean shouldShowOptOutPromo();
 
@@ -136,6 +139,9 @@ public class NewTabPageView extends FrameLayout
         /** Opens a given URL in the current tab. */
         void open(String url);
 
+        /** Opens the interests dialog. */
+        void navigateToInterests();
+
         /**
          * Animates the search box up into the omnibox and bring up the keyboard.
          * @param beginVoiceSearch Whether to begin a voice search.
@@ -306,6 +312,12 @@ public class NewTabPageView extends FrameLayout
                 mManager.navigateToBookmarks();
             }
         });
+        toolbar.getInterestsButton().setOnClickListener(new View.OnClickListener() {
+            @Override
+            public void onClick(View v) {
+                mManager.navigateToInterests();
+            }
+        });
 
         initializeSearchBoxScrollHandling();
         addOnLayoutChangeListener(this);
@@ -340,6 +352,13 @@ public class NewTabPageView extends FrameLayout
                 }
             });
         }
+
+        // Set up interests
+        // TODO(peconn): If the user is not signed in, show Interests button that leads to sign-in.
+        if (CommandLine.getInstance().hasSwitch(ChromeSwitches.ENABLE_NTP_INTERESTS)

[newt (away), 2015/12/14 21:18:39]

Better: add a method isInterestsEnabled() in NewTabPage manager, and put both
the signed in and command line check into the method.

[PEConn, 2015/12/15 11:50:15]

Done.

+                && manager.isUserSignedIn()) {
+            toolbar.getInterestsButton().setVisibility(View.VISIBLE);
+        }
     }
 
     private int getTabsMovedIllustration() {