Adds check/set for first_active_omaha_ping_sent (from vpd).

first_active_omaha_ping_sent is a boolean in RW_VPD that is checked to
decide whether to send the first active ping (a=-1) to omaha. update_engine
reads its value and sets it to "true" after first active ping is sent or
if the first ping has been sent already and it does not exits in the vpd
(to capture the same feature for older devices).

BUG=chromium:717788
TEST=cros_workon_make --test; Deployed on a device and made sure the
flag is read and writen properly.
CQ-DEPEND=CL:469126

Change-Id: I867d16de1d5d2da4d7a7e1f26aa8e951d90b68f2
Reviewed-on: https://chromium-review.googlesource.com/469107
Commit-Ready: Amin Hassani <ahassani@chromium.org>
Tested-by: Amin Hassani <ahassani@chromium.org>
Reviewed-by: Andrew de los Reyes <adlr@chromium.org>
diff --git a/common/fake_hardware.h b/common/fake_hardware.h
index 5d0fca3..01d23d0 100644
--- a/common/fake_hardware.h
+++ b/common/fake_hardware.h
@@ -81,6 +81,14 @@
     return false;
   }
 
+  bool GetFirstActiveOmahaPingSent() const override {
+    return first_active_omaha_ping_sent_;
+  }
+
+  void SetFirstActiveOmahaPingSent() override {
+    first_active_omaha_ping_sent_ = true;
+  }
+
   // Setters
   void SetIsOfficialBuild(bool is_official_build) {
     is_official_build_ = is_official_build;
@@ -137,6 +145,7 @@
   std::string ec_version_{"Fake EC v1.0a"};
   int powerwash_count_{kPowerwashCountNotSet};
   bool powerwash_scheduled_{false};
+  bool first_active_omaha_ping_sent_{false};
 
   DISALLOW_COPY_AND_ASSIGN(FakeHardware);
 };