[NTP] Do not reload the MV tiles on theme change

This is a remnant from when the tile icon images were generated with a
(dark) gray background, depending on the system theme. Now that the tile
background controlled via CSS, it's no longer required to reload the
tiles when the background image is changed in dark mode.

Bug: 986935
Change-Id: Iccd076f354a838e9025856151e1e486824ed4c4d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1716100Reviewed-by: Kyle Milka <kmilka@chromium.org>
Commit-Queue: Kristi Park <kristipark@chromium.org>
Cr-Commit-Position: refs/heads/master@{#680316}

chrome/browser/resources/local_ntp/local_ntp.js

@@ -248,13 +248,6 @@ let ntpApiHandle;
  */
 let isDarkModeEnabled = false;
 
-/**
- * True if dark colored chips should be used instead of light mode chips when
- * dark mode is enabled.
- * @type {boolean}
- */
-let useDarkChips = false;
-
 /**
  * Returns a timeout that can be executed early. Calls back true if this was
  * an early execution, false otherwise.
@@ -353,8 +346,7 @@ function renderTheme() {
 
   // Update dark mode styling.
   isDarkModeEnabled = window.matchMedia('(prefers-color-scheme: dark)').matches;
-  useDarkChips = getUseDarkChips(info);
-  document.body.classList.toggle('light-chip', !useDarkChips);
+  document.body.classList.toggle('light-chip', !getUseDarkChips(info));
 
   const background = [
     convertToRGBAColor(info.backgroundColorRgba), info.imageUrl,
@@ -493,18 +485,9 @@ function renderOneGoogleBarTheme() {
  * Callback for embeddedSearch.newTabPage.onthemechange.
  */
 function onThemeChange() {
-  // Save the current dark mode state to check if dark mode has changed.
-  const usingDarkChips = useDarkChips;
-
   renderTheme();
   renderOneGoogleBarTheme();
   sendThemeInfoToMostVisitedIframe();
-
-  // If dark mode has been changed, refresh the MV tiles to render the
-  // appropriate icon.
-  if (usingDarkChips != useDarkChips) {
-    reloadTiles();
-  }
 }
 
 /**

chrome/browser/ui/search/local_ntp_browsertest.cc

@@ -995,11 +995,8 @@ IN_PROC_BROWSER_TEST_F(LocalNTPDarkModeTest, ToggleDarkMode) {
   ASSERT_TRUE(GetIsLightChipsApplied(active_tab));
 
   // Enable dark mode and wait until the MV tiles have updated.
-  content::DOMMessageQueue msg_queue(active_tab);
   theme()->SetDarkMode(true);
   theme()->NotifyObservers();
-  local_ntp_test_utils::WaitUntilTilesLoaded(active_tab, &msg_queue,
-                                             /*delay=*/0);
 
   // Check that dark mode has been properly applied.
   EXPECT_TRUE(GetIsDarkModeApplied(active_tab));
@@ -1008,11 +1005,8 @@ IN_PROC_BROWSER_TEST_F(LocalNTPDarkModeTest, ToggleDarkMode) {
   EXPECT_FALSE(GetIsLightChipsApplied(active_tab));
 
   // Disable dark mode and wait until the MV tiles have updated.
-  msg_queue.ClearQueue();
   theme()->SetDarkMode(false);
   theme()->NotifyObservers();
-  local_ntp_test_utils::WaitUntilTilesLoaded(active_tab, &msg_queue,
-                                             /*delay=*/0);
 
   // Check that dark mode has been removed.
   EXPECT_FALSE(GetIsDarkModeApplied(active_tab));