Move instant support to SearchTabHelper.

chrome/browser/ui/search/instant_controller.cc

Index: chrome/browser/ui/search/instant_controller.cc
diff --git a/chrome/browser/ui/search/instant_controller.cc b/chrome/browser/ui/search/instant_controller.cc
index 02ba4d3c6a367e313050d415e01b35bf01b8838f..c2bab79753c3dfdf4803907c10588272e4f1968f 100644
--- a/chrome/browser/ui/search/instant_controller.cc
+++ b/chrome/browser/ui/search/instant_controller.cc
@@ -971,7 +971,9 @@ void InstantController::SearchModeChanged(const SearchMode& old_mode,
   if (!new_mode.is_search_suggestions())
     HideOverlay();
 
-  ResetInstantTab();
+  // Now that the overlay is hidden, try |instant_tab_| again.

[samarth, 2013/05/08 02:38:48]

Let's take out all the instant tab resetting logic out of this CL and focus on
the instant support determined bit.

[kmadhusu, 2013/05/09 02:40:40]

Done.

+  if (!instant_tab_)
+    ResetInstantTab();
 }
 
 void InstantController::ActiveTabChanged() {
@@ -1523,12 +1525,20 @@ void InstantController::ResetInstantTab() {
     if (!instant_tab_ || active_tab != instant_tab_->contents()) {
       instant_tab_.reset(new InstantTab(this));
       instant_tab_->Init(active_tab);
-      UpdateInfoForInstantTab();
-      use_tab_for_suggestions_ = true;
+      // Note that |instant_tab_| may have gotten reset in Init() if it's
+      // already known to not support instant.
+      if (instant_tab_) {
+        UpdateInfoForInstantTab();
+        use_tab_for_suggestions_ = true;
+      } else {
+        use_tab_for_suggestions_ = false;
+      }
     }
 
-    // Hide the |overlay_| since we are now using |instant_tab_| instead.
-    HideOverlay();
+    if (instant_tab_) {
+      // Hide the |overlay_| since we are now using |instant_tab_| instead.
+      HideOverlay();
+    }
   } else {
     instant_tab_.reset();
   }
@@ -1589,8 +1599,12 @@ void InstantController::ShowOverlay(int height, InstantSizeUnits units) {
   // HideOverlay()) so that it can change its mind.
   if (height == 0) {
     model_.SetOverlayState(SearchMode(), 0, INSTANT_SIZE_PERCENT);
-    if (instant_tab_)
+    if (instant_tab_) {
       use_tab_for_suggestions_ = true;
+    } else {
+      // Now that the overlay is hidden, try |instant_tab_| again.
+      ResetInstantTab();
+    }
     return;
   }