Instant: Use only one hidden WebContents per profile.

chrome/browser/ui/cocoa/tab_contents/instant_overlay_controller_mac.mm

Index: chrome/browser/ui/cocoa/tab_contents/instant_overlay_controller_mac.mm
diff --git a/chrome/browser/ui/cocoa/tab_contents/instant_overlay_controller_mac.mm b/chrome/browser/ui/cocoa/tab_contents/instant_overlay_controller_mac.mm
index 059b05d14a47acbdbf8b6885e55bb4daee8304b4..e13a12e783c61cb1c0f62e18f493682fd042aea7 100644
--- a/chrome/browser/ui/cocoa/tab_contents/instant_overlay_controller_mac.mm
+++ b/chrome/browser/ui/cocoa/tab_contents/instant_overlay_controller_mac.mm
@@ -22,22 +22,21 @@ InstantOverlayControllerMac::~InstantOverlayControllerMac() {
 
 void InstantOverlayControllerMac::OverlayStateChanged(
     const InstantOverlayModel& model) {
-  if (model.mode().is_ntp() || model.mode().is_search_suggestions()) {
-    // Drop shadow is only needed if search mode is not |NTP| and overlay does
-    // not fill up the entire contents page.
-    BOOL drawDropShadow = !model.mode().is_ntp() &&
-        !(model.height() == 100 &&
-          model.height_units() == INSTANT_SIZE_PERCENT);
-    [overlay_ setOverlay:model.GetOverlayContents()
+  if (model.contents()) {
+    // Drop shadow is only needed if the overlay does not fill up the entire
+    // contents page. TODO(sail): Compute the actual height, a la Views code.
+    BOOL drawDropShadow =
+        model.height() != 100 || model.height_units() != INSTANT_SIZE_PERCENT;
+    [overlay_ setOverlay:model.contents()
                   height:model.height()
              heightUnits:model.height_units()
           drawDropShadow:drawDropShadow];
+    browser_->MaybeUpdateBookmarkBarStateForInstantOverlay();
   } else {
     [overlay_ setOverlay:NULL
                   height:0
              heightUnits:INSTANT_SIZE_PIXELS
           drawDropShadow:NO];
   }
-  browser_->MaybeUpdateBookmarkBarStateForInstantOverlay(model.mode());
   [window_ updateBookmarkBarStateForInstantOverlay];
 }