Restrict update_engine SSL certs.

update_engine connects over SSL only with Google servers, so we
restrict the list of SSL certificates to a smaller list, used by
Google.

Bug: 25089263
Test: mma
Change-Id: I73dbbd18dd99a61fa3bd66dbb57d0ff1ab78160d
diff --git a/common/platform_constants_android.cc b/common/platform_constants_android.cc
index f35d7ef..4f55106 100644
--- a/common/platform_constants_android.cc
+++ b/common/platform_constants_android.cc
@@ -27,7 +27,7 @@
 const char kOmahaPlatformName[] = "Brillo";
 const char kUpdatePayloadPublicKeyPath[] =
     "/etc/update_engine/update-payload-key.pub.pem";
-const char kCACertificatesPath[] = "/system/etc/security/cacerts";
+const char kCACertificatesPath[] = "/system/etc/security/cacerts_google";
 // No deadline file API support on Android.
 const char kOmahaResponseDeadlineFile[] = "";
 const char kNonVolatileDirectory[] = "/data/misc/update_engine";