Merge remote-tracking branch 'goog/upstream-master'.

The following commits were reverted:
840703a Fix update over cellular network on guest account
eaad5d0 Do not merge to AOSP: Fixes the link to brillo-clang-format in CrOS
740efad Reboot even if a system update is not available.

Fixed a few sign compare warnings.
Had to ifdef out 2 SquashfsFilesystemTest because it depends on unsquashfs -m.

Test: update_engine_unittests
Change-Id: I6f4ca5003e78c76064ec60d0797505d8c18d00bf
Merged-In: I6f4ca5003e78c76064ec60d0797505d8c18d00bf

common/hardware_interface.h

diff --git a/common/hardware_interface.h b/common/hardware_interface.h
index c9e2f85..94442d1 100644
--- a/common/hardware_interface.h
+++ b/common/hardware_interface.h
@@ -94,6 +94,15 @@
 
   // Returns the timestamp of the current OS build.
   virtual int64_t GetBuildTimestamp() const = 0;
+
+  // Returns whether the first active ping was sent to Omaha at some point, and
+  // that the value is persisted across recovery (and powerwash) once set with
+  // |SetFirstActiveOmahaPingSent()|.
+  virtual bool GetFirstActiveOmahaPingSent() const = 0;
+
+  // Persist the fact that first active ping was sent to omaha. It bails out if
+  // it fails.
+  virtual void SetFirstActiveOmahaPingSent() = 0;
 };
 
 }  // namespace chromeos_update_engine