Implement direct write fallback proxy

content/common/dwrite_font_proxy_messages.h

Index: content/common/dwrite_font_proxy_messages.h
diff --git a/content/common/dwrite_font_proxy_messages.h b/content/common/dwrite_font_proxy_messages.h
index cc8aced1dec3a14f2452cba92d6a7c900e3a1cb0..288a3cf0d05cb300b8ff35a0499e567997b3afed 100644
--- a/content/common/dwrite_font_proxy_messages.h
+++ b/content/common/dwrite_font_proxy_messages.h
@@ -23,6 +23,20 @@ typedef std::pair<base::string16, base::string16> DWriteStringPair;
 
 #endif  // CONTENT_COMMON_DWRITE_FONT_PROXY_MESSAGES_H_
 
+IPC_STRUCT_BEGIN(DWriteFontStyle)
+  IPC_STRUCT_MEMBER(uint16_t, font_weight)
+  IPC_STRUCT_MEMBER(uint8_t, font_slant)
+  IPC_STRUCT_MEMBER(uint8_t, font_stretch)
+IPC_STRUCT_END()
+
+IPC_STRUCT_BEGIN(MapCharactersResult)
+  IPC_STRUCT_MEMBER(uint32_t, family_index)
+  IPC_STRUCT_MEMBER(base::string16, family_name)
+  IPC_STRUCT_MEMBER(uint32_t, mapped_length)
+  IPC_STRUCT_MEMBER(float, scale)
+  IPC_STRUCT_MEMBER(DWriteFontStyle, font_style)

[scottmg, 2016/04/13 21:23:16]

font_style doesn't seem to be used in OnMapCharacters()?

[Ilya Kulshin, 2016/04/13 22:31:29]

Nice catch! Apparently DirectWrite doesn't care if I feed it all zeroes, but
good to preserve the style all the same.

+IPC_STRUCT_END()
+
 // Locates the index of the specified font family within the system collection.
 IPC_SYNC_MESSAGE_CONTROL1_1(DWriteFontProxyMsg_FindFamily,
                             base::string16 /* family_name */,
@@ -44,3 +58,18 @@ IPC_SYNC_MESSAGE_CONTROL1_1(
 IPC_SYNC_MESSAGE_CONTROL1_1(DWriteFontProxyMsg_GetFontFiles,
                             uint32_t /* family_index */,
                             std::vector<base::string16> /* out file_paths */)
+
+// Locates a font family that is able to render the specified text using the
+// specified style. If successful, the family_index and family_name will
+// indicate which family in the system font collection can render the requested
+// text and the mapped_length will indicate how many characters can be
+// rendered. If no font exists that can render the text, family_index will be
+// UINT32_MAX and mapped_length will indicate how many characters cannot be
+// rendered by any installed font.
+IPC_SYNC_MESSAGE_CONTROL5_1(DWriteFontProxyMsg_MapCharacters,
+                            base::string16 /* text */,
+                            DWriteFontStyle /* font_style */,
+                            base::string16 /* locale_name */,
+                            uint32_t /* reading_direction */,
+                            base::string16 /* base_family_name - optional */,
+                            MapCharactersResult /* out */)