Initialize FontConfigIPC when zygote is disabled so font fallback works.

content/browser/renderer_host/sandbox_ipc_linux.h

Index: content/browser/renderer_host/sandbox_ipc_linux.h
diff --git a/content/browser/renderer_host/sandbox_ipc_linux.h b/content/browser/renderer_host/sandbox_ipc_linux.h
index 3d9e98de331ba0d525499f2b1fd1b54f77e4afdb..0a6b97fa7cf78cd1bf36085721871547c187a526 100644
--- a/content/browser/renderer_host/sandbox_ipc_linux.h
+++ b/content/browser/renderer_host/sandbox_ipc_linux.h
@@ -7,13 +7,17 @@
 #ifndef CONTENT_BROWSER_RENDERER_HOST_SANDBOX_IPC_LINUX_H_
 #define CONTENT_BROWSER_RENDERER_HOST_SANDBOX_IPC_LINUX_H_
 
+#include <stdint.h>
+
 #include <memory>
+#include <string>
 #include <vector>
 
 #include "base/files/scoped_file.h"
 #include "base/macros.h"
 #include "base/pickle.h"
 #include "base/threading/simple_thread.h"
+#include "content/common/content_export.h"
 
 class SkString;
 
@@ -29,6 +33,15 @@ class SandboxIPCHandler : public base::DelegateSimpleThread::Delegate {
 
   void Run() override;
 
+  class TestObserver {
+   public:
+    virtual void OnGetFallbackFontForChar(UChar32 c,
+                                          std::string name,
+                                          int id) = 0;
+    virtual void OnFontOpen(int id) = 0;
+  };
+  CONTENT_EXPORT static void SetObserverForTests(TestObserver* observer);
+
  private:
   int FindOrAddPath(const SkString& path);