Implement --force-variation-ids

- Adds a new flag --force-variation-ids
- Accepts a comma-separated list of numeric experiment ids.
- Strictly meant for dev use.
- Basic error checking for invalid flags based on StringToInt behavior.

BUG=305882

Review URL: https://codereview.chromium.org/26565007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@228406 0039d316-1c4b-4281-b951-d872f2087c98

3 files changed, 101 insertions, 5 deletions

diff --git a/chrome/browser/metrics/variations/variations_http_header_provider.cc b/chrome/browser/metrics/variations/variations_http_header_provider.cc
index 10f2173..20b3e719 100644
--- a/chrome/browser/metrics/variations/variations_http_header_provider.cc
+++ b/chrome/browser/metrics/variations/variations_http_header_provider.cc
@@ -4,9 +4,13 @@
 
 #include "chrome/browser/metrics/variations/variations_http_header_provider.h"
 
+#include <vector>
+
 #include "base/base64.h"
 #include "base/memory/singleton.h"
 #include "base/metrics/histogram.h"
+#include "base/strings/string_number_conversions.h"
+#include "base/strings/string_split.h"
 #include "base/strings/string_util.h"
 #include "chrome/browser/google/google_util.h"
 #include "chrome/common/metrics/proto/chrome_experiments.pb.h"
@@ -53,6 +57,23 @@ void VariationsHttpHeaderProvider::AppendHeaders(
   }
 }
 
+bool VariationsHttpHeaderProvider::SetDefaultVariationIds(
+    const std::string& variation_ids) {
+  default_variation_ids_set_.clear();
+  std::vector<std::string> entries;
+  base::SplitString(variation_ids, ',', &entries);
+  for (std::vector<std::string>::const_iterator it = entries.begin();
+       it != entries.end(); ++it) {
+    int variation_id = 0;
+    if (!base::StringToInt(*it, &variation_id)) {
+      default_variation_ids_set_.clear();
+      return false;
+    }
+    default_variation_ids_set_.insert(variation_id);
+  }
+  return true;
+}
+
 VariationsHttpHeaderProvider::VariationsHttpHeaderProvider()
     : variation_ids_cache_initialized_(false) {
 }
@@ -113,21 +134,27 @@ void VariationsHttpHeaderProvider::UpdateVariationIDsHeaderValue() {
 
   // The header value is a serialized protobuffer of Variation IDs which is
   // base64 encoded before transmitting as a string.
-  if (variation_ids_set_.empty())
+  variation_ids_header_.clear();
+
+  if (variation_ids_set_.empty() && default_variation_ids_set_.empty())
     return;
 
   // This is the bottleneck for the creation of the header, so validate the size
   // here. Force a hard maximum on the ID count in case the Variations server
   // returns too many IDs and DOSs receiving servers with large requests.
   DCHECK_LE(variation_ids_set_.size(), 10U);
-  if (variation_ids_set_.size() > 20) {
-    variation_ids_header_.clear();
+  if (variation_ids_set_.size() > 20)
     return;
-  }
 
-  metrics::ChromeVariations proto;
+  // Merge the two sets of experiment ids.
+  std::set<VariationID> all_variation_ids_set = default_variation_ids_set_;
   for (std::set<VariationID>::const_iterator it = variation_ids_set_.begin();
        it != variation_ids_set_.end(); ++it) {
+    all_variation_ids_set.insert(*it);
+  }
+  metrics::ChromeVariations proto;
+  for (std::set<VariationID>::const_iterator it = all_variation_ids_set.begin();
+       it != all_variation_ids_set.end(); ++it) {
     proto.add_variation_id(*it);
   }
 
diff --git a/chrome/browser/metrics/variations/variations_http_header_provider.h b/chrome/browser/metrics/variations/variations_http_header_provider.h
index b432572..96e5f26 100644
--- a/chrome/browser/metrics/variations/variations_http_header_provider.h
+++ b/chrome/browser/metrics/variations/variations_http_header_provider.h
@@ -46,11 +46,21 @@ class VariationsHttpHeaderProvider : base::FieldTrialList::Observer {
                      bool uma_enabled,
                      net::HttpRequestHeaders* headers);
 
+  // Sets *additional* variation ids to be encoded in the X-Chrome-Varations
+  // request header.  This is intended for development use to force a server
+  // side experiment id.  |variation_ids| should be a comma-separated string of
+  // numeric experiment ids.
+  bool SetDefaultVariationIds(const std::string& variation_ids);
+
  private:
   friend struct DefaultSingletonTraits<VariationsHttpHeaderProvider>;
 
   FRIEND_TEST_ALL_PREFIXES(VariationsHttpHeaderProviderTest,
                            ShouldAppendHeaders);
+  FRIEND_TEST_ALL_PREFIXES(VariationsHttpHeaderProviderTest,
+                           SetDefaultVariationIds_Valid);
+  FRIEND_TEST_ALL_PREFIXES(VariationsHttpHeaderProviderTest,
+                           SetDefaultVariationIds_Invalid);
 
   VariationsHttpHeaderProvider();
   virtual ~VariationsHttpHeaderProvider();
@@ -86,6 +96,9 @@ class VariationsHttpHeaderProvider : base::FieldTrialList::Observer {
   // Keep a cache of variation IDs that are transmitted in headers to Google.
   // This consists of a list of valid IDs, and the actual transmitted header.
   std::set<chrome_variations::VariationID> variation_ids_set_;
+
+  // Provides the google experiment ids forced from command line.
+  std::set<chrome_variations::VariationID> default_variation_ids_set_;
   std::string variation_ids_header_;
 
   DISALLOW_COPY_AND_ASSIGN(VariationsHttpHeaderProvider);
diff --git a/chrome/browser/metrics/variations/variations_http_header_provider_unittest.cc b/chrome/browser/metrics/variations/variations_http_header_provider_unittest.cc
index 9e997f9..6d5be7e 100644
--- a/chrome/browser/metrics/variations/variations_http_header_provider_unittest.cc
+++ b/chrome/browser/metrics/variations/variations_http_header_provider_unittest.cc
@@ -4,11 +4,35 @@
 
 #include "chrome/browser/metrics/variations/variations_http_header_provider.h"
 
+#include <string>
+
+#include "base/base64.h"
+#include "base/message_loop/message_loop.h"
+#include "chrome/common/metrics/proto/chrome_experiments.pb.h"
+#include "net/http/http_request_headers.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "url/gurl.h"
 
 namespace chrome_variations {
 
+namespace {
+
+// Decodes the variations header and extracts the variation ids.
+bool ExtractVariationIds(const std::string& variations,
+                       std::set<VariationID>* variation_ids) {
+  std::string serialized_proto;
+  if (!base::Base64Decode(variations, &serialized_proto))
+    return false;
+  metrics::ChromeVariations proto;
+  if (!proto.ParseFromString(serialized_proto))
+    return false;
+  for (int i = 0; i < proto.variation_id_size(); ++i)
+    variation_ids->insert(proto.variation_id(i));
+  return true;
+}
+
+}  // namespace
+
 TEST(VariationsHttpHeaderProviderTest, ShouldAppendHeaders) {
   struct {
     const char* url;
@@ -39,4 +63,36 @@ TEST(VariationsHttpHeaderProviderTest, ShouldAppendHeaders) {
   }
 }
 
+TEST(VariationsHttpHeaderProviderTest, SetDefaultVariationIds_Valid) {
+  base::MessageLoop loop;
+  VariationsHttpHeaderProvider provider;
+  GURL url("http://www.google.com");
+  net::HttpRequestHeaders headers;
+  std::string variations;
+
+  // Valid experiment ids.
+  EXPECT_TRUE(provider.SetDefaultVariationIds("12,456"));
+  provider.InitVariationIDsCacheIfNeeded();
+  provider.AppendHeaders(url, false, false, &headers);
+  EXPECT_TRUE(headers.HasHeader("X-Chrome-Variations"));
+  headers.GetHeader("X-Chrome-Variations", &variations);
+  std::set<VariationID> variation_ids;
+  ASSERT_TRUE(ExtractVariationIds(variations, &variation_ids));
+  EXPECT_TRUE(variation_ids.find(12) != variation_ids.end());
+  EXPECT_TRUE(variation_ids.find(456) != variation_ids.end());
+}
+
+TEST(VariationsHttpHeaderProviderTest, SetDefaultVariationIds_Invalid) {
+  base::MessageLoop loop;
+  VariationsHttpHeaderProvider provider;
+  GURL url("http://www.google.com");
+  net::HttpRequestHeaders headers;
+
+  // Invalid experiment ids.
+  EXPECT_FALSE(provider.SetDefaultVariationIds("abcd12,456"));
+  provider.InitVariationIDsCacheIfNeeded();
+  provider.AppendHeaders(url, false, false, &headers);
+  EXPECT_FALSE(headers.HasHeader("X-Chrome-Variations"));
+}
+
 }  // namespace chrome_variations