Reland of This CL replaces e-mail with AccountId on user selection screen. (patchset #1 id:1 of https://codereview.chromium.org/1454153002/ )

Reason for revert:
This did not fix issues, reverting the revert.

Original issue's description:
> Revert of This CL replaces e-mail with AccountId on user selection screen. (patchset #12 id:220001 of https://codereview.chromium.org/1440583002/ )
>
> Reason for revert:
> Suspecting this CL for introducing failures on Mac 10.10 Release (ATI)
>
> First failure: https://build.chromium.org/p/chromium.gpu/builders/Mac%2010.10%20Release%20%28ATI%29/builds/8148
>
> Failing tests:
> CastStreamingApiTestWithPixelOutput.EndToEnd
> TabCaptureApiPixelTest.EndToEndThroughWebRTC
> TabCaptureApiPixelTest.EndToEndWithoutRemoting
>
> Please update tests.
>
> Original issue's description:
> > This CL replaces e-mail with AccountId on user selection screen.
> >
> > This CL replaces e-mail with serialized AccountId on user selection screen.
> > It also adds simple AccountId Serialize/Deserialize methods suitable for
> > passing AccountId to JS code.
> >
> > This is part of transition to AccountId.
> >
> > BUG=462823, 552034
> > TEST=manual
> >
> > Committed: https://crrev.com/1e24fe57a4ca921355bb1506f5a79627647a8c16
> > Cr-Commit-Position: refs/heads/master@{#360319}
>
> TBR=dzhioev@chromium.org,rogerta@chromium.org,stevenjb@chromium.org,oshima@chromium.org,alemate@chromium.org
> NOPRESUBMIT=true
> NOTREECHECKS=true
> NOTRY=true
> BUG=462823, 552034
>
> Committed: https://crrev.com/dede4c3836de2dddda5a484f098bba7152a6779b
> Cr-Commit-Position: refs/heads/master@{#360369}

TBR=dzhioev@chromium.org,rogerta@chromium.org,stevenjb@chromium.org,oshima@chromium.org,alemate@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=462823, 552034

Review URL: https://codereview.chromium.org/1455263002

Cr-Commit-Position: refs/heads/master@{#360423}

2 files changed, 55 insertions, 2 deletions

diff --git a/components/signin/core/account_id/account_id.cc b/components/signin/core/account_id/account_id.cc
index 65b237f..e933f4b 100644
--- a/components/signin/core/account_id/account_id.cc
+++ b/components/signin/core/account_id/account_id.cc
@@ -6,7 +6,10 @@
 
 #include <functional>
 
+#include "base/json/json_reader.h"
+#include "base/json/json_writer.h"
 #include "base/memory/singleton.h"
+#include "base/values.h"
 #include "google_apis/gaia/gaia_auth_util.h"
 
 namespace {
@@ -14,6 +17,10 @@ namespace {
 // Known account types.
 const char kGoogle[] = "google";
 
+// Serialization keys
+const char kGaiaIdKey[] = "gaia_id";
+const char kEmailKey[] = "email";
+
 struct GoogleStringSingleton {
   GoogleStringSingleton() : google(kGoogle) {}
 
@@ -115,6 +122,47 @@ AccountId AccountId::FromUserEmailGaiaId(const std::string& email,
   return AccountId(gaia_id, email);
 }
 
+std::string AccountId::Serialize() const {
+  base::DictionaryValue value;
+  value.SetString(kGaiaIdKey, gaia_id_);
+  value.SetString(kEmailKey, user_email_);
+
+  std::string serialized;
+  base::JSONWriter::Write(value, &serialized);
+  return serialized;
+}
+
+// static
+bool AccountId::Deserialize(const std::string& serialized,
+                            AccountId* account_id) {
+  base::JSONReader reader;
+  scoped_ptr<const base::Value> value(reader.Read(serialized));
+  const base::DictionaryValue* dictionary_value = NULL;
+
+  if (!value || !value->GetAsDictionary(&dictionary_value))
+    return false;
+
+  std::string gaia_id;
+  std::string user_email;
+
+  const bool found_gaia_id = dictionary_value->GetString(kGaiaIdKey, &gaia_id);
+  const bool found_user_email =
+      dictionary_value->GetString(kEmailKey, &user_email);
+
+  if (!found_gaia_id)
+    LOG(ERROR) << "gaia_id is not found in '" << serialized << "'";
+
+  if (!found_user_email)
+    LOG(ERROR) << "user_email is not found in '" << serialized << "'";
+
+  if (!found_gaia_id && !found_user_email)
+    return false;
+
+  *account_id = FromUserEmailGaiaId(user_email, gaia_id);
+
+  return true;
+}
+
 const AccountId& EmptyAccountId() {
   return AccountId::EmptyAccountId::GetInstance()->user_id;
 }
diff --git a/components/signin/core/account_id/account_id.h b/components/signin/core/account_id/account_id.h
index 73be450..9f72030 100644
--- a/components/signin/core/account_id/account_id.h
+++ b/components/signin/core/account_id/account_id.h
@@ -45,8 +45,13 @@ class AccountId {
   static AccountId FromUserEmailGaiaId(const std::string& user_email,
                                        const std::string& gaia_id);
 
-  // std::string Serialize() const;
-  // static AccountId Deserialize(const std::string& serialized);
+  // These are (for now) unstable and cannot be used to store serialized data to
+  // persistent storage. Only in-memory storage is safe.
+  // Serialize() returns JSON dictionary,
+  // Deserialize() restores AccountId after serialization.
+  std::string Serialize() const;
+  static bool Deserialize(const std::string& serialized,
+                          AccountId* out_account_id);
 
  private:
   AccountId();