Refactor OriginTrialPolicy to be an abstract interface in content/public/common

content/shell/common/shell_content_client.h

Index: content/shell/common/shell_content_client.h
diff --git a/content/shell/common/shell_content_client.h b/content/shell/common/shell_content_client.h
index 1b80e0f799e31c89a17aecd657d0216cb0dcbb34..1c22125caeeb99886a550a695637689294f6c01e 100644
--- a/content/shell/common/shell_content_client.h
+++ b/content/shell/common/shell_content_client.h
@@ -10,6 +10,8 @@
 
 #include "base/compiler_specific.h"
 #include "content/public/common/content_client.h"
+#include "content/public/common/origin_trial_policy.h"
+#include "content/shell/common/shell_origin_trial_policy.h"
 
 namespace content {
 
@@ -29,10 +31,10 @@ class ShellContentClient : public ContentClient {
       int resource_id) const override;
   gfx::Image& GetNativeImageNamed(int resource_id) const override;
   bool IsSupplementarySiteIsolationModeEnabled() override;
-  base::StringPiece GetOriginTrialPublicKey() override;
+  OriginTrialPolicy* GetOriginTrialPolicy() override;
 
  private:
-  base::StringPiece origin_trial_public_key_;
+  ShellOriginTrialPolicy origin_trial_policy_;
 };
 
 }  // namespace content