Move instant support to SearchTabHelper. Fix InstantTab reset.

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 e721a26e45e908da47226ad37f3c128f8caf0cf6..44d9ee2b2dca4990ca840c21204e6c4927d54b9e 100644
--- a/chrome/browser/ui/search/instant_controller.cc
+++ b/chrome/browser/ui/search/instant_controller.cc
@@ -1452,18 +1452,23 @@ void InstantController::ResetInstantTab() {
     if (!instant_tab_ || active_tab != instant_tab_->contents()) {
       instant_tab_.reset(new InstantTab(this));
       instant_tab_->Init(active_tab);
-      // Update theme info for this tab.
-      browser_->UpdateThemeInfo();
-      instant_tab_->SetDisplayInstantResults(instant_enabled_);
-      instant_tab_->SetOmniboxBounds(omnibox_bounds_);
-      instant_tab_->InitializeFonts();
-      StartListeningToMostVisitedChanges();
-      instant_tab_->KeyCaptureChanged(
-          omnibox_focus_state_ == OMNIBOX_FOCUS_INVISIBLE);
+      // Note that |instant_tab_| may have gotten reset in Init() if it's
+      // already known to not support instant.
+      if (instant_tab_) {
+        // Update theme info for this tab.
+        browser_->UpdateThemeInfo();
+        instant_tab_->SetDisplayInstantResults(instant_enabled_);
+        instant_tab_->SetOmniboxBounds(omnibox_bounds_);
+        instant_tab_->InitializeFonts();
+        StartListeningToMostVisitedChanges();
+        instant_tab_->KeyCaptureChanged(
+            omnibox_focus_state_ == OMNIBOX_FOCUS_INVISIBLE);
+      }
     }
 
     // Hide the |overlay_| since we are now using |instant_tab_| instead.
-    HideOverlay();
+    if (instant_tab_)
+      HideOverlay();
   } else {
     instant_tab_.reset();
   }
@@ -1489,6 +1494,10 @@ void InstantController::HideInternal() {
     overlay_->Update(string16(), 0, 0, true);
   }
 
+  // Now that the overlay is hidden, try |instant_tab_| again.
+  if (!instant_tab_)
+    ResetInstantTab();
+
   // Clear the first interaction timestamp for later use.
   first_interaction_time_ = base::Time();
 }
@@ -1509,6 +1518,11 @@ 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);
+
+    // Now that the overlay is hidden, try |instant_tab_| again.
+    if (!instant_tab_)
+      ResetInstantTab();
+
     return;
   }