[Chrome Colors] Update color picker value only on open.

No need to update color picker value while its open. As theme updates
have latency, it only creates unsmooth behavior as theme updates try to
update the color picker color while sliding over the color spectrum.

Bug: 990379
Change-Id: I6feaabee66ecbbc15b70b26037224a8655c69f1c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1749424Reviewed-by: Kristi Park <kristipark@chromium.org>
Commit-Queue: Gayane Petrosyan <gayane@chromium.org>
Cr-Commit-Position: refs/heads/master@{#686557}

chrome/browser/resources/local_ntp/customize.js

@@ -304,6 +304,13 @@ customize.preselectedOptions = {
  */
 customize.colorsMenuLoaded = false;
 
+
+/**
+ * Custom color picked in hex format.
+ * @type {string}
+ */
+customize.customColorPicked = '#000000';
+
 /**
  * Sets the visibility of the settings menu and individual options depending on
  * their respective features.
@@ -2259,6 +2266,7 @@ customize.loadColorsMenu = function() {
   // Configure custom color picker.
   if (configData.chromeColorsCustomColorPicker) {
     $(customize.IDS.COLOR_PICKER_TILE).onclick = function(event) {
+      $(customize.IDS.COLOR_PICKER).value = customize.customColorPicked;
       $(customize.IDS.COLOR_PICKER).click();
     };
     $(customize.IDS.COLOR_PICKER_TILE).onkeydown =
@@ -2321,8 +2329,7 @@ customize.colorsMenuPreselectTile = function() {
     tile = $(customize.IDS.COLOR_PICKER_TILE);
 
     // Update color picker tile colors.
-    $(customize.IDS.COLOR_PICKER).value =
-        colorArrayToHex(themeInfo.colorPicked);
+    customize.customColorPicked = colorArrayToHex(themeInfo.colorPicked);
     $(customize.IDS.COLORS_MENU)
         .style.setProperty(
             '--custom-color-border', colorArrayToHex(themeInfo.colorDark));