Omnibox UI Experiments: Add vertical margin variations to about:flags

This CL implements it on Views only. There will be a followup to do
the variation on Mac.

BUG=717777

Review-Url: https://codereview.chromium.org/2854263002
Cr-Commit-Position: refs/heads/master@{#470050}
diff --git a/chrome/browser/about_flags.cc b/chrome/browser/about_flags.cc
index cdaea04b..174c87c5 100644
--- a/chrome/browser/about_flags.cc
+++ b/chrome/browser/about_flags.cc
@@ -966,6 +966,29 @@
      switches::kEnableHeapProfiling,
      switches::kEnableHeapProfilingTaskProfiler}};
 
+const FeatureEntry::FeatureParam kOmniboxUIVerticalMargin4px[] = {
+    {OmniboxFieldTrial::kUIExperimentsVerticalMarginParam, "4"}};
+const FeatureEntry::FeatureParam kOmniboxUIVerticalMargin8px[] = {
+    {OmniboxFieldTrial::kUIExperimentsVerticalMarginParam, "8"}};
+const FeatureEntry::FeatureParam kOmniboxUIVerticalMargin12px[] = {
+    {OmniboxFieldTrial::kUIExperimentsVerticalMarginParam, "12"}};
+const FeatureEntry::FeatureParam kOmniboxUIVerticalMargin16px[] = {
+    {OmniboxFieldTrial::kUIExperimentsVerticalMarginParam, "16"}};
+const FeatureEntry::FeatureParam kOmniboxUIVerticalMargin20px[] = {
+    {OmniboxFieldTrial::kUIExperimentsVerticalMarginParam, "20"}};
+
+const FeatureEntry::FeatureVariation kOmniboxUIVerticalMarginVariations[] = {
+    {"4px vertical margin", kOmniboxUIVerticalMargin4px,
+     arraysize(kOmniboxUIVerticalMargin4px), nullptr},
+    {"8px vertical margin", kOmniboxUIVerticalMargin8px,
+     arraysize(kOmniboxUIVerticalMargin8px), nullptr},
+    {"12px vertical margin", kOmniboxUIVerticalMargin12px,
+     arraysize(kOmniboxUIVerticalMargin12px), nullptr},
+    {"16px vertical margin", kOmniboxUIVerticalMargin16px,
+     arraysize(kOmniboxUIVerticalMargin16px), nullptr},
+    {"20px vertical margin", kOmniboxUIVerticalMargin20px,
+     arraysize(kOmniboxUIVerticalMargin20px), nullptr}};
+
 // RECORDING USER METRICS FOR FLAGS:
 // -----------------------------------------------------------------------------
 // The first line of the entry is the internal name.
@@ -2838,6 +2861,13 @@
      SINGLE_VALUE_TYPE(switches::kShowCertLink)},
 #endif
 
+    {"omnibox-ui-vertical-margin",
+     flag_descriptions::kOmniboxUIVerticalMarginName,
+     flag_descriptions::kOmniboxUIVerticalMarginDescription, kOsDesktop,
+     FEATURE_WITH_PARAMS_VALUE_TYPE(omnibox::kUIExperiments,
+                                    kOmniboxUIVerticalMarginVariations,
+                                    "OmniboxUIVerticalMarginVariations")},
+
     {"use-suggestions-even-if-few",
      flag_descriptions::kUseSuggestionsEvenIfFewFeatureName,
      flag_descriptions::kUseSuggestionsEvenIfFewFeatureDescription, kOsAll,