Ensure that the DirectWrite font cache works in Chrome canary on Windows 8+ with AppContainer prote…

content/common/sandbox_win.cc

Index: content/common/sandbox_win.cc
diff --git a/content/common/sandbox_win.cc b/content/common/sandbox_win.cc
index 8398b798d06080dd6cd0e9281ad07005c95b49a8..91f81c3a43942aab98268c943a5dc828a6470b54 100644
--- a/content/common/sandbox_win.cc
+++ b/content/common/sandbox_win.cc
@@ -11,9 +11,11 @@
 #include "base/debug/profiler.h"
 #include "base/files/file_util.h"
 #include "base/hash.h"
+#include "base/memory/shared_memory.h"
 #include "base/metrics/sparse_histogram.h"
 #include "base/path_service.h"
 #include "base/process/launch.h"
+#include "base/strings/string_number_conversions.h"
 #include "base/strings/string_util.h"
 #include "base/strings/stringprintf.h"
 #include "base/trace_event/trace_event.h"
@@ -24,6 +26,7 @@
 #include "content/common/content_switches_internal.h"
 #include "content/public/common/content_client.h"
 #include "content/public/common/content_switches.h"
+#include "content/public/common/dwrite_font_platform_win.h"
 #include "content/public/common/sandbox_init.h"
 #include "content/public/common/sandboxed_process_launcher_delegate.h"
 #include "sandbox/win/src/process_mitigations.h"
@@ -677,6 +680,22 @@ base::Process StartSandboxedProcess(
                   true,
                   sandbox::TargetPolicy::FILES_ALLOW_READONLY,
                   policy);
+
+      // If DirectWrite is enabled for font rendering then open the font cache
+      // section which is created by the browser and pass the handle to the
+      // renderer process. This is needed because renderer processes on
+      // Windows 8+ may be running in an AppContainer sandbox and hence their
+      // kernel object namespace may be partitioned.
+      std::string name(content::kFontCacheSharedSectionName);
+      name.append(base::UintToString(base::GetCurrentProcId()));
+
+      base::SharedMemory direct_write_font_cache_section;
+      if (direct_write_font_cache_section.Open(name, true)) {
+        HANDLE shared_handle =

[cpu_(ooo_6.6-7.5), 2015/05/08 03:03:24]

use void*, we don't want future coder to try to close it.

[ananta, 2015/05/08 19:08:19]

Done.

+            policy->AddHandleToShare(direct_write_font_cache_section.handle());
+        cmd_line->AppendSwitchASCII(switches::kFontCacheSharedHandle,
+            base::UintToString(reinterpret_cast<unsigned int>(shared_handle)));
+      }
     }

[cpu_(ooo_6.6-7.5), 2015/05/08 03:03:24]

is this code working? after the renderer process is launched, this process ends
up with no handles to the shared section, so the section is opened in the
renderer but not in the browser.

Do you mean to open the section every time a renderer is opened? I was expecting
you to do the opening only once.

[ananta, 2015/05/08 04:10:18]

The shared section is created by the browser via a call to
content::LoadCacheFile. It remains valid for the duration of the process. The
open here is fine and should work for each renderer.

 #endif
   } else {