Updates subpixel positioning and hinting when DSF is changed

ui/gfx/font_render_params_linux.cc

Index: ui/gfx/font_render_params_linux.cc
diff --git a/ui/gfx/font_render_params_linux.cc b/ui/gfx/font_render_params_linux.cc
index 34afe6fb3ade7ee4527acfd37aabb8d19626d96d..f4cd346e80fb8427a36bf5580e7361c00a705be8 100644
--- a/ui/gfx/font_render_params_linux.cc
+++ b/ui/gfx/font_render_params_linux.cc
@@ -61,9 +61,10 @@ struct SynchronizedCache {
 base::LazyInstance<SynchronizedCache>::Leaky g_synchronized_cache =
     LAZY_INSTANCE_INITIALIZER;
 
-bool IsBrowserTextSubpixelPositioningEnabled() {
+bool IsBrowserTextSubpixelPositioningEnabled(
+    const FontRenderParamsQuery& query) {
 #if defined(OS_CHROMEOS)
-  return device_scale_factor_for_internal_display > 1.0f;
+  return query.device_scale_factor > 1.0f;
 #else
   return false;
 #endif
@@ -179,16 +180,22 @@ bool QueryFontconfig(const FontRenderParamsQuery& query,
 // Serialize |query| into a string and hash it to a value suitable for use as a
 // cache key.
 uint32 HashFontRenderParamsQuery(const FontRenderParamsQuery& query) {
-  return base::Hash(base::StringPrintf("%d|%d|%d|%d|%s",
-      query.for_web_contents, query.pixel_size, query.point_size, query.style,
-      JoinString(query.families, ',').c_str()));
+  return base::Hash(base::StringPrintf(
+      "%d|%d|%d|%d|%s|%f", query.for_web_contents, query.pixel_size,
+      query.point_size, query.style, JoinString(query.families, ',').c_str(),
+      query.device_scale_factor));
 }
 
 }  // namespace
 
 FontRenderParams GetFontRenderParams(const FontRenderParamsQuery& query,
                                      std::string* family_out) {
-  const uint32 hash = HashFontRenderParamsQuery(query);
+  FontRenderParamsQuery actual_query(query);
+#if defined(OS_CHROMEOS)
+  if (actual_query.device_scale_factor == 0)
+    actual_query.device_scale_factor = device_scale_factor_for_internal_display;
+#endif
+  const uint32 hash = HashFontRenderParamsQuery(actual_query);
   SynchronizedCache* synchronized_cache = g_synchronized_cache.Pointer();
 
   {
@@ -213,7 +220,7 @@ FontRenderParams GetFontRenderParams(const FontRenderParamsQuery& query,
   const LinuxFontDelegate* delegate = LinuxFontDelegate::instance();
   if (delegate)
     params = delegate->GetDefaultFontRenderParams();
-  QueryFontconfig(query, &params, family_out);
+  QueryFontconfig(actual_query, &params, family_out);
   if (!params.antialiasing) {
     // Cairo forces full hinting when antialiasing is disabled, since anything
     // less than that looks awful; do the same here. Requesting subpixel
@@ -225,10 +232,10 @@ FontRenderParams GetFontRenderParams(const FontRenderParamsQuery& query,
     // Fontconfig doesn't support configuring subpixel positioning; check a
     // flag.
     params.subpixel_positioning =
-        query.for_web_contents ?
-        CommandLine::ForCurrentProcess()->HasSwitch(
-            switches::kEnableWebkitTextSubpixelPositioning) :
-        IsBrowserTextSubpixelPositioningEnabled();
+        actual_query.for_web_contents
+            ? CommandLine::ForCurrentProcess()->HasSwitch(
+                  switches::kEnableWebkitTextSubpixelPositioning)
+            : IsBrowserTextSubpixelPositioningEnabled(actual_query);
 
     // To enable subpixel positioning, we need to disable hinting.
     if (params.subpixel_positioning)
@@ -236,8 +243,8 @@ FontRenderParams GetFontRenderParams(const FontRenderParamsQuery& query,
   }
 
   // Use the first family from the list if Fontconfig didn't suggest a family.
-  if (family_out && family_out->empty() && !query.families.empty())
-    *family_out = query.families[0];
+  if (family_out && family_out->empty() && !actual_query.families.empty())
+    *family_out = actual_query.families[0];
 
   {
     // Store the result. It's fine if this overwrites a result that was cached
@@ -257,6 +264,10 @@ void ClearFontRenderParamsCacheForTest() {
 }
 
 #if defined(OS_CHROMEOS)
+float GetFontRenderParamsDeviceScaleFactor() {
+  return device_scale_factor_for_internal_display;
+}
+
 void SetFontRenderParamsDeviceScaleFactor(float device_scale_factor) {
   device_scale_factor_for_internal_display = device_scale_factor;
 }