blink fonts: Load Android SkFontMgr on Linux.

content/zygote/zygote_main_linux.cc

Index: content/zygote/zygote_main_linux.cc
diff --git a/content/zygote/zygote_main_linux.cc b/content/zygote/zygote_main_linux.cc
index c30e1084a92c6eecaf07417f30c3d5464b9b0f8a..37314abed831b35e91101ddc18ea3b2382fe39c4 100644
--- a/content/zygote/zygote_main_linux.cc
+++ b/content/zygote/zygote_main_linux.cc
@@ -46,6 +46,7 @@
 #include "sandbox/linux/services/namespace_sandbox.h"
 #include "sandbox/linux/services/thread_helpers.h"
 #include "sandbox/linux/suid/client/setuid_sandbox_client.h"
+#include "third_party/WebKit/public/web/linux/WebFontRendering.h"

[no sievers, 2016/02/22 22:27:20]

Although there is no DEPS file, it feels a bit odd to have renderer-specific is
in here.
+jln@

 #include "third_party/icu/source/i18n/unicode/timezone.h"
 #include "third_party/skia/include/ports/SkFontConfigInterface.h"
 
@@ -67,6 +68,8 @@
 #include <sanitizer/coverage_interface.h>
 #endif
 
+#include "third_party/skia/include/ports/SkFontMgr_android.h"

[no sievers, 2016/02/22 22:27:20]

Is 'port' meant to be public?

[Khushal, 2016/02/22 23:46:00]

I think so. We do use the SkFontConfigInterface port here already.

+
 namespace content {
 
 namespace {
@@ -344,8 +347,32 @@ static void ZygotePreSandboxInit() {
 #if defined(ENABLE_WEBRTC)
   InitializeWebRtcModule();
 #endif
+
   SkFontConfigInterface::SetGlobal(
       new FontConfigIPC(GetSandboxFD()))->unref();

[no sievers, 2016/02/22 22:27:20]

Isn't this the way to get around the sandbox on Linux?

[Khushal, 2016/02/22 23:46:00]

We actually needed to use the android specific implementation in this case which
currently assumes access to the file system for font files.
A similar approach to manage the sandbox is used with RAND_set_urandom_fd too.

+
+  // Set the android SkFontMgr for blink. We need to ensure this is done
+  // before the sandbox is initialized to allow the font manager to access
+  // font configuration files on disk.
+  if (base::CommandLine::ForCurrentProcess()->HasSwitch(
+      switches::kAndroidFontsLocation)) {
+    std::string android_fonts_dir =
+        base::CommandLine::ForCurrentProcess()->GetSwitchValueASCII(
+            switches::kAndroidFontsLocation);
+
+    if (android_fonts_dir.size() > 0 && android_fonts_dir.back() != '/')
+      android_fonts_dir += '/';
+    std::string font_config = android_fonts_dir + "fonts.xml";
+    SkFontMgr_Android_CustomFonts custom = {
+        SkFontMgr_Android_CustomFonts::SystemFontUse::kOnlyCustom,
+        android_fonts_dir.c_str(),
+        font_config.c_str(),
+        nullptr,
+        true,
+    };
+
+    blink::WebFontRendering::setSkiaFontManager(SkFontMgr_New_Android(&custom));

[no sievers, 2016/02/22 22:27:20]

Isn't this an implementation detail that it only uses the directory during
construction?

[Khushal, 2016/02/22 23:46:00]

We added a mode to the public API to make sure that it uses the directory only
during construction for this case. The custom flags expose this functionality as
a part of the public API now.

+  }
 }
 
 static bool CreateInitProcessReaper(base::Closure* post_fork_parent_callback) {