Compress variations_seed pref in Local State.

Compressed size is 0.22% of the original size, resulting
in much less space used in Local State.

Keeps code to fallback to reading the older pref around,
for a few releases, so that seeds don't get reset.

Also:
  - Adds a histogram to track seed store results.
  - Removes VLOGs which can now be debugged with
    the above histogram.
  - Deletes obsolete kVariationsSeedHash pref code.

BUG=457315

Review URL: https://codereview.chromium.org/903483003

Cr-Commit-Position: refs/heads/master@{#315899}

2 files changed, 7 insertions, 0 deletions

diff --git a/chrome/installer/util/master_preferences.cc b/chrome/installer/util/master_preferences.cc
index 2c08b1f..bcb6b8b 100644
--- a/chrome/installer/util/master_preferences.cc
+++ b/chrome/installer/util/master_preferences.cc
@@ -292,6 +292,10 @@ bool MasterPreferences::GetExtensionsBlock(
       master_preferences::kExtensionsBlock, extensions);
 }
 
+std::string MasterPreferences::GetCompressedVariationsSeed() const {
+  return ExtractPrefString(prefs::kVariationsCompressedSeed);
+}
+
 std::string MasterPreferences::GetVariationsSeed() const {
   return ExtractPrefString(prefs::kVariationsSeed);
 }
diff --git a/chrome/installer/util/master_preferences.h b/chrome/installer/util/master_preferences.h
index 9a7355e..2b8c914 100644
--- a/chrome/installer/util/master_preferences.h
+++ b/chrome/installer/util/master_preferences.h
@@ -156,6 +156,9 @@ class MasterPreferences {
   //
   bool GetExtensionsBlock(base::DictionaryValue** extensions) const;
 
+  // Returns the compressed variations seed entry from the master prefs.
+  std::string GetCompressedVariationsSeed() const;
+
   // Returns the variations seed entry from the master prefs.
   std::string GetVariationsSeed() const;