alternate ntp: implement Show/HideBars API to reduce jank when showing/hiding bars

chrome/browser/instant/search.h

Index: chrome/browser/instant/search.h
diff --git a/chrome/browser/instant/search.h b/chrome/browser/instant/search.h
index 41ce390a3bbed60565214b41e72b2018f5a8d73a..68aa61442320f711950d8baac2f7ca89a00f05d8 100644
--- a/chrome/browser/instant/search.h
+++ b/chrome/browser/instant/search.h
@@ -18,6 +18,12 @@ class Profile;
 class TemplateURL;
 class TemplateURLRef;
 
+namespace chrome {
+namespace search {
+struct Mode;
+}
+}
+
 namespace content {
 class NavigationEntry;
 class WebContents;
@@ -150,6 +156,11 @@ bool GetBoolValueForFlagWithDefault(const std::string& flag,
 GURL CoerceCommandLineURLToTemplateURL(const GURL& instant_url,
                                        const TemplateURLRef& ref);
 
+// Returns true if visibility change in top bars should be handled based on
+// |old_mode| and |new_mode|.
+bool ShouldHandleTopBarsVisibilityChange(const Mode& old_mode,

[dhollowa, 2013/03/13 17:21:55]

This should live in search_model.h/cc.  And how about renaming to
|ShouldChangeTopBarsVisibility|?

[kuan, 2013/03/13 22:21:07]

Done.

+                                         const Mode& new_mode);
+
 }  // namespace search
 }  // namespace chrome