Scanning: Style "Scan" header

Spec: http://shortn/_O6M4tRc5EQ
Screenshot: http://shortn/_mosolq202i

Bug: 1059779
Test: browser_tests --gtest_filter=ScanningAppBrowserTest.All
Change-Id: Icb29009332fea0de87eefacd82259ab695109a21
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2506302
Commit-Queue: Michael Checo <michaelcheco@google.com>
Reviewed-by: Zentaro Kavanagh <zentaro@chromium.org>
Reviewed-by: Jimmy Gong <jimmyxgong@chromium.org>
Cr-Commit-Position: refs/heads/master@{#823552}

chromeos/components/scanning/resources/scanning_app.html

 <style include="cr-shared-style scanning-shared scanning-fonts">
+  #appTitle {
+    @apply --scanning-section-title-font;
+    color: var(--scanning-section-title-text-color);
+  }
+
   #moreSettingsButton {
     --ink-color: var(--menu-text-color);
     --paper-ripple-opacity: 0;

chromeos/components/scanning/resources/scanning_fonts_css.html

@@ -2,16 +2,24 @@
   <style>
     :host {
       --scanning-more-settings-font-family: Roboto;
+      --scanning-section-title-font-family: "Google Sans", Roboto, sans-serif;
       --scanning-select-font-family: Roboto;
 
       --scanning-chevron-icon-font-size: 20px;
       --scanning-more-settings-font-size: 12px;
+      --scanning-section-title-font-size: 22px;
       --scanning-select-font-size: 13px;
 
       --scanning-chevron-icon-color: var(--google-grey-700);
       --scanning-more-settings-text-color: var(--google-grey-700);
+      --scanning-section-title-text-color: var(--google-grey-900);
       --scanning-select-text-color: var(--google-grey-900);
 
+      --scanning-section-title-font: {
+        font-family: var(--scanning-section-title-font-family);
+        font-size: var(--scanning-section-title-font-size);
+      }
+
       --scanning-select-font: {
           font-family: var(--scanning-select-font-family);
           font-size: var(--scanning-select-font-size);