Reland 2: mac: Use a placeholder string for the family name of the system font.

Source/core/layout/LayoutTextControlSingleLine.cpp

Index: Source/core/layout/LayoutTextControlSingleLine.cpp
diff --git a/Source/core/layout/LayoutTextControlSingleLine.cpp b/Source/core/layout/LayoutTextControlSingleLine.cpp
index bf8ec2b730dad4147596d39d95d85dae3816184b..494b3ef3d982127b83ab80274ba92b6b59b2ca72 100644
--- a/Source/core/layout/LayoutTextControlSingleLine.cpp
+++ b/Source/core/layout/LayoutTextControlSingleLine.cpp
@@ -299,11 +299,13 @@ LayoutRect LayoutTextControlSingleLine::controlClipRect(const LayoutPoint& addit
 
 float LayoutTextControlSingleLine::getAvgCharWidth(const AtomicString& family) const
 {
-    // Since Lucida Grande is the default font, we want this to match the width
-    // of MS Shell Dlg, the default font for textareas in Firefox, Safari Win and
-    // IE for some encodings (in IE, the default font is encoding specific).
-    // 901 is the avgCharWidth value in the OS/2 table for MS Shell Dlg.
-    if (family == "Lucida Grande")
+    // Match the default system font to the width of MS Shell Dlg, the default
+    // font for textareas in Firefox, Safari Win and IE for some encodings (in
+    // IE, the default font is encoding specific). 901 is the avgCharWidth value
+    // in the OS/2 table for MS Shell Dlg.
+    // This is a hack which Blink no longer applies on OSX 10.10+.

[tkent, 2015/08/11 05:24:48]

nit: This line looks redundant because LayoutThemeMac.mm has it.

[erikchen, 2015/08/11 05:30:02]

Done.

+    // https://code.google.com/p/chromium/issues/detail?id=515989#c8
+    if (LayoutTheme::theme().needsHackForTextControlWithFontFamily(family))
         return scaleEmToUnits(901);
 
     return LayoutTextControl::getAvgCharWidth(family);
@@ -320,11 +322,13 @@ LayoutUnit LayoutTextControlSingleLine::preferredContentLogicalWidth(float charW
 
     float maxCharWidth = 0.f;
     AtomicString family = styleRef().font().fontDescription().family().family();
-    // Since Lucida Grande is the default font, we want this to match the width
-    // of MS Shell Dlg, the default font for textareas in Firefox, Safari Win and
-    // IE for some encodings (in IE, the default font is encoding specific).
-    // 4027 is the (xMax - xMin) value in the "head" font table for MS Shell Dlg.
-    if (family == "Lucida Grande")
+    // Match the default system font to the width of MS Shell Dlg, the default
+    // font for textareas in Firefox, Safari Win and IE for some encodings (in
+    // IE, the default font is encoding specific). 4027 is the (xMax - xMin)
+    // value in the "head" font table for MS Shell Dlg.
+    // This is a hack which Blink no longer applies on OSX 10.10+.

[tkent, 2015/08/11 05:24:48]

Ditto.

[erikchen, 2015/08/11 05:30:02]

Done.

+    // https://code.google.com/p/chromium/issues/detail?id=515989#c8
+    if (LayoutTheme::theme().needsHackForTextControlWithFontFamily(family))
         maxCharWidth = scaleEmToUnits(4027);
     else if (hasValidAvgCharWidth(family))
         maxCharWidth = roundf(styleRef().font().primaryFont()->maxCharWidth());