[jumbo] Merge two identical kFaviconsPerCategoryImage constants

In some jumbo build experiments (not official) there was an
identical constant in two explore_sites files. In jumbo builds
many cc files are merged into one translation unit for much
faster compilation.

This moves the constant to a header where it can be reused.

Change-Id: Id460645a39d69999bf2227c25651d1149f1a6d6c
Reviewed-on: https://chromium-review.googlesource.com/c/1275895
Commit-Queue: Justin DeWitt <dewittj@chromium.org>
Reviewed-by: Justin DeWitt <dewittj@chromium.org>
Cr-Commit-Position: refs/heads/master@{#600172}

chrome/browser/android/explore_sites/explore_sites_service_impl.cc

@@ -23,9 +23,6 @@ using chrome::android::explore_sites::ExploreSitesVariation;
 using chrome::android::explore_sites::GetExploreSitesVariation;
 
 namespace explore_sites {
-namespace {
-const int kFaviconsPerCategoryImage = 4;
-}
 
 ExploreSitesServiceImpl::ExploreSitesServiceImpl(
     std::unique_ptr<ExploreSitesStore> store,

chrome/browser/android/explore_sites/explore_sites_types.h

@@ -16,6 +16,8 @@
 #include "url/gurl.h"
 
 namespace explore_sites {
+constexpr int kFaviconsPerCategoryImage = 4;
+
 // The in-memory representation of a site in the ExploreSitesStore.
 // Image data is not represented here because it is requested separately from
 // the UI layer.

chrome/browser/android/explore_sites/image_helper.cc

@@ -19,8 +19,6 @@
 
 namespace explore_sites {
 namespace {
-const int kFaviconsPerCategoryImage = 4;
-
 // Ratio of icon size to the amount of padding between the icons.
 const int kIconPaddingScale = 8;
 }  // namespace