[Cleanup] Factor out common code.

chrome/browser/ui/chrome_pages.cc

Index: chrome/browser/ui/chrome_pages.cc
diff --git a/chrome/browser/ui/chrome_pages.cc b/chrome/browser/ui/chrome_pages.cc
index 179c0bb9bc2c8e19209f385eda61c6e9e92b2df9..1ab515ff0842a6a6d39ab34aaf6cefeb451fe4ab 100644
--- a/chrome/browser/ui/chrome_pages.cc
+++ b/chrome/browser/ui/chrome_pages.cc
@@ -134,6 +134,26 @@ std::string GenerateContentSettingsExceptionsSubPage(ContentSettingsType type) {
 
 }  // namespace
 
+bool IsInternalPage(const GURL& url) {
+  // TODO(groby): Figure out if TabManager/session restore rely on this
+  // being a shortened list, or if all WebUI pages qualify.
+
+  // There are many chrome:// UI URLs, but only look for the ones that users
+  // are likely to have open. Most of the benefit is from the NTP URL.
+  const char* const kReloadableUrlPrefixes[] = {
+      chrome::kChromeUIDownloadsURL, chrome::kChromeUIHistoryURL,
+      chrome::kChromeUINewTabURL, chrome::kChromeUISettingsURL,
+  };
+  // Prefix-match against the table above. Use strncmp to avoid allocating
+  // memory to convert the URL prefix constants into std::strings.
+  for (size_t i = 0; i < arraysize(kReloadableUrlPrefixes); ++i) {
+    if (!strncmp(url.spec().c_str(), kReloadableUrlPrefixes[i],
+                 strlen(kReloadableUrlPrefixes[i])))
+      return true;
+  }
+  return false;
+}
+
 void ShowBookmarkManager(Browser* browser) {
   content::RecordAction(UserMetricsAction("ShowBookmarkManager"));
   content::RecordAction(UserMetricsAction("ShowBookmarks"));