diff --git a/common/constants.cc b/common/constants.cc
index 5ab96b0..87bdf91 100644
--- a/common/constants.cc
+++ b/common/constants.cc
@@ -126,4 +126,10 @@
 
 const char kOmahaUpdaterVersion[] = "0.1.0.0";
 
+// X-Goog-Update headers.
+const char kXGoogleUpdateInteractivity[] = "X-Goog-Update-Interactivity";
+const char kXGoogleUpdateAppId[] = "X-Goog-Update-AppId";
+const char kXGoogleUpdateUpdater[] = "X-Goog-Update-Updater";
+const char kXGoogleUpdateSessionId[] = "X-Goog-SessionId";
+
 }  // namespace chromeos_update_engine
diff --git a/common/constants.h b/common/constants.h
index 9b4623f..d95a56a 100644
--- a/common/constants.h
+++ b/common/constants.h
@@ -110,6 +110,12 @@
 
 extern const char kOmahaUpdaterVersion[];
 
+// X-Goog-Update headers.
+extern const char kXGoogleUpdateInteractivity[];
+extern const char kXGoogleUpdateAppId[];
+extern const char kXGoogleUpdateUpdater[];
+extern const char kXGoogleUpdateSessionId[];
+
 // A download source is any combination of protocol and server (that's of
 // interest to us when looking at UMA metrics) using which we may download
 // the payload.
diff --git a/common/file_fetcher.h b/common/file_fetcher.h
index fbdfc32..bd39007 100644
--- a/common/file_fetcher.h
+++ b/common/file_fetcher.h
@@ -59,6 +59,12 @@
   void SetHeader(const std::string& header_name,
                  const std::string& header_value) override {}
 
+  bool GetHeader(const std::string& header_name,
+                 std::string* header_value) const override {
+    header_value->clear();
+    return false;
+  }
+
   // Suspend the asynchronous file read.
   void Pause() override;
 
diff --git a/common/http_fetcher.h b/common/http_fetcher.h
index 93b0e24..94f31d7 100644
--- a/common/http_fetcher.h
+++ b/common/http_fetcher.h
@@ -100,6 +100,14 @@
   virtual void SetHeader(const std::string& header_name,
                          const std::string& header_value) = 0;
 
+  // Only used for testing.
+  // If |header_name| is set, the value will be set into |header_value|.
+  // On success the boolean true will be returned, hoewever on failture to find
+  // the |header_name| in the header the return value will be false. The state
+  // in which |header_value| is left in for failures is an empty string.
+  virtual bool GetHeader(const std::string& header_name,
+                         std::string* header_value) const = 0;
+
   // If data is coming in too quickly, you can call Pause() to pause the
   // transfer. The delegate will not have ReceivedBytes() called while
   // an HttpFetcher is paused.
diff --git a/common/mock_http_fetcher.h b/common/mock_http_fetcher.h
index 492e6ce..0f04319 100644
--- a/common/mock_http_fetcher.h
+++ b/common/mock_http_fetcher.h
@@ -89,6 +89,12 @@
   void SetHeader(const std::string& header_name,
                  const std::string& header_value) override;
 
+  bool GetHeader(const std::string& header_name,
+                 std::string* header_value) const override {
+    header_value->clear();
+    return false;
+  }
+
   // Return the value of the header |header_name| or the empty string if not
   // set.
   std::string GetHeader(const std::string& header_name) const;
diff --git a/common/multi_range_http_fetcher.h b/common/multi_range_http_fetcher.h
index f57ea7f..ef32f0d 100644
--- a/common/multi_range_http_fetcher.h
+++ b/common/multi_range_http_fetcher.h
@@ -83,6 +83,11 @@
     base_fetcher_->SetHeader(header_name, header_value);
   }
 
+  bool GetHeader(const std::string& header_name,
+                 std::string* header_value) const override {
+    return base_fetcher_->GetHeader(header_name, header_value);
+  }
+
   void Pause() override { base_fetcher_->Pause(); }
 
   void Unpause() override { base_fetcher_->Unpause(); }