Fix default font used in VR text element

The VR code is using the default font "sans-serif".
The Font (and FontList) on that platform is the PlatformFontSkia
When creating the font with the literal "sans-serif", there is
not matched typeface.

The function creating the typeface has a fallback path that try
"sans" which is the resulting typeface used.

see: https://cs.chromium.org/chromium/src/ui/gfx/platform_font_skia.cc?l=53

This CL avoid to use that fallback logic. Instead, we rely on
the FontList behavior to use the default system font with the default
constructor.


R=alcooper@chromium.org

Change-Id: I612502f32d77787b8f0346c0fc23cd65b68e3013
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1847902Reviewed-by: Klaus Weidner <klausw@chromium.org>
Commit-Queue: Etienne Bergeron <etienneb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#704279}

chrome/browser/vr/elements/text.cc

@@ -24,7 +24,6 @@ namespace {
 constexpr float kCursorWidthRatio = 0.07f;
 constexpr int kTextPixelPerDmm = 1100;
 constexpr float kTextShadowScaleFactor = 1000.0f;
-constexpr char kDefaultFontFamily[] = "sans-serif";
 
 int DmmToPixel(float dmm) {
   return static_cast<int>(dmm * kTextPixelPerDmm);
@@ -389,8 +388,9 @@ gfx::Size TextTexture::LayOutText() {
     text_bounds.set_width(DmmToPixel(text_width_));
   }
 
-  gfx::FontList fonts =
-      gfx::FontList(gfx::Font(kDefaultFontFamily, pixel_font_height));
+  gfx::FontList fonts;
+  if (fonts.GetFontSize() != pixel_font_height)
+    fonts = fonts.DeriveWithSizeDelta(pixel_font_height - fonts.GetFontSize());
 
   TextRenderParameters parameters;
   parameters.color = color_;