Update Data Saver chart background

Bug: 945906
Change-Id: I4b085fa0a7f62b7b331ae99a48fb0a3dd5d46422
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1547533Reviewed-by: Theresa <twellington@chromium.org>
Commit-Queue: Sinan Sahin <sinansahin@google.com>
Cr-Commit-Position: refs/heads/master@{#646580}

chrome/android/java/res/values/colors.xml

@@ -95,7 +95,7 @@
     <!-- Data Saver Colors -->
     <color name="data_reduction_compressed_color">#E1E1E1</color>
     <color name="data_reduction_original_color">@color/pref_accent_color</color>
-    <color name="data_reduction_chart_background_color">@color/modern_grey_50</color>
+    <color name="data_reduction_chart_background_color">@color/modern_secondary_color</color>
 
     <!-- Compositor Tab Title Colors -->
     <color name="compositor_tab_title_bar_text">@color/default_text_color</color>