[Home] Check if expand button enabled before setting visibility

When a URL focus is in progress, we reset toolbar button visibility.
The expand button visibility needs to be guarded on whether the button
is enabled.

BUG=725392

Review-Url: https://codereview.chromium.org/2896303002
Cr-Commit-Position: refs/heads/master@{#473980}

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

@@ -626,9 +626,12 @@ public class BottomToolbarPhone extends ToolbarPhone {
                 mToolbarButtonsContainer.setVisibility(View.VISIBLE);
                 mToolbarButtonsContainer.setTranslationX(0);
 
+                if (!mUseToolbarHandle) {
                     mExpandButton.setAlpha(1.f);
                     mExpandButton.setVisibility(View.VISIBLE);
                     mExpandButton.setTranslationX(0);
+                }
+
                 requestLayout();
             } else {
                 mToolbarButtonVisibilityPercent = 0.f;