Add "Dotum" to the noSubpixelForSmallSizeFont black list

This patch disables kSubpixelPositioning_Flag for "Dotum" in small
sizes.

The embedded bitmap of "Dotum" font looks poorly positioned when linear
metrics is used. This patch improves the positioning of the font by
disabling linear metrics.

Skia disables linear metrics and use DWRITE_MEASURING_MODE_GDI_CLASSIC
when kEmbeddedBitmapText_Flag & the font has 'eblc' OpenType table for
the specified size & !kSubpixelPositioning_Flag. The first two
conditions are already true, this patch turns the last condition to
true.

BUG=394585

Review URL: https://codereview.chromium.org/1304363011

git-svn-id: svn://svn.chromium.org/blink/trunk@201515 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/Source/platform/fonts/win/FontCacheSkiaWin.cpp

@@ -403,6 +403,7 @@ FontPlatformData* FontCache::createFontPlatformData(const FontDescription& fontD
         L"arial",
         L"comic sans",
         L"courier new",
+        L"dotum",
         L"georgia",
         L"impact",
         L"lucida console",