Reland of Use only toolbar to transition from fakebox to real omnibox.

chrome/android/java/src/org/chromium/chrome/browser/toolbar/ToolbarTablet.java

Index: chrome/android/java/src/org/chromium/chrome/browser/toolbar/ToolbarTablet.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/toolbar/ToolbarTablet.java b/chrome/android/java/src/org/chromium/chrome/browser/toolbar/ToolbarTablet.java
index 2ccefe712e54428283d129d44751f583a389ca6d..eb62dce888250ad0d4d4c6698980c3bda2bc448a 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/toolbar/ToolbarTablet.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/toolbar/ToolbarTablet.java
@@ -21,6 +21,7 @@
 import org.chromium.chrome.browser.ChromeSwitches;
 import org.chromium.chrome.browser.NavigationPopup;
 import org.chromium.chrome.browser.device.DeviceClassManager;
+import org.chromium.chrome.browser.ntp.NewTabPage;
 import org.chromium.chrome.browser.omnibox.LocationBar;
 import org.chromium.chrome.browser.omnibox.LocationBarTablet;
 import org.chromium.chrome.browser.partnercustomizations.HomepageManager;
@@ -68,6 +69,8 @@
     private final int mStartPaddingWithoutButtons;
     private boolean mShouldAnimateButtonVisibilityChange;
     private AnimatorSet mButtonVisibilityAnimators;
+
+    private NewTabPage mVisibleNtp;
 
     /**
      * Constructs a ToolbarTablet object.
@@ -337,6 +340,38 @@
             }
             mUseLightColorAssets = incognito;
         }
+
+        updateNtp();
+    }
+
+    /**
+     * Called when the currently visible New Tab Page changes.
+     */
+    private void updateNtp() {
+        NewTabPage newVisibleNtp = getToolbarDataProvider().getNewTabPageForCurrentTab();
+        if (mVisibleNtp == newVisibleNtp) return;
+
+        if (mVisibleNtp != null) {
+            mVisibleNtp.setSearchBoxScrollListener(null);
+        }
+        mVisibleNtp = newVisibleNtp;
+        if (mVisibleNtp != null) {
+            mVisibleNtp.setSearchBoxScrollListener(new NewTabPage.OnSearchBoxScrollListener() {
+                @Override
+                public void onNtpScrollChanged(float scrollPercentage) {
+                    // Fade the search box out in the first 40% of the scrolling transition.
+                    float alpha = Math.max(1f - scrollPercentage * 2.5f, 0f);
+                    mVisibleNtp.setSearchBoxAlpha(alpha);
+                    mVisibleNtp.setSearchProviderLogoAlpha(alpha);
+                }
+            });
+        }
+    }
+
+    @Override
+    protected void onTabContentViewChanged() {
+        super.onTabContentViewChanged();
+        updateNtp();
     }
 
     @Override