linux: Cache GetFontRenderParams() results.

ui/gfx/font_render_params.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef UI_GFX_FONT_RENDER_PARAMS_H_
 #define UI_GFX_FONT_RENDER_PARAMS_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 73 matching lines @@
   int style;
 };
 
 // Returns the appropriate parameters for rendering the font described by
 // |query|. If |family_out| is non-NULL, it will be updated to contain the
 // recommended font family from |query.families|.
 GFX_EXPORT FontRenderParams GetFontRenderParams(
     const FontRenderParamsQuery& query,
     std::string* family_out);
 
+// Clears GetFontRenderParams()'s cache. Intended to be called by tests that are
+// changing Fontconfig's configuration.
+GFX_EXPORT void DropFontRenderParamsCacheForTest();

[Daniel Erat, 2014/08/04 23:44:43]

i'm getting "undeclared identifier" errors that i don't understand when i hide
this behind "#if defined(OS_LINUX)" -- presumably that indicates that OS_LINUX
isn't defined when font_render_params_linux_unittest.cc includes this file,
which doesn't make sense to me. i could spend more time trying to figure out
what's going on there, or add no-op implementations for non-linux platforms, or
add a comment mentioning that this is only defined for linux.

[msw, 2014/08/05 00:55:10]

nit: s/Drop/Clear/

[msw, 2014/08/05 00:55:10]

That seems very odd to me as well... would you mind uploading a patch set with
the preprocessor checks you wish to add and see if the trybots or I can help at
all? Otherwise, just adding a comment for now seems fine.

[Daniel Erat, 2014/08/06 17:43:11]

Done.

[Daniel Erat, 2014/08/06 17:43:11]

sure, uploaded. and i can see with an #error that OS_LINUX is in fact not
defined here.

[msw, 2014/08/06 19:31:38]

Acknowledged; the comment is fine.

+
 }  // namespace gfx
 
 #endif  // UI_GFX_FONT_RENDER_PARAMS_H_