WPT for WebView: fix title to show up correctly

The title text's bg color is black, so changing the font color to be
white such that the title text can show correctly.

Bug: 994939
Change-Id: Ib1728893d18c729fadd26b83efdf639bf41a4fa2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1789478
Commit-Queue: Changwan Ryu <changwan@chromium.org>
Reviewed-by: Andrew Luo <aluo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#694458}

android_webview/tools/system_webview_shell/apk/res/layout/activity_web_platform_tests_child.xml

@@ -37,6 +37,7 @@
         android:ellipsize="end"
         android:maxLines="1"
         android:textStyle="bold"
+        android:textColor="@android:color/white"
         />
   </LinearLayout>
 </LinearLayout>
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