Migrate HostZoomMap to live in StoragePartition.

content/public/test/mock_render_process_host.cc

Index: content/public/test/mock_render_process_host.cc
diff --git a/content/public/test/mock_render_process_host.cc b/content/public/test/mock_render_process_host.cc
index 1f5de5f22faadcfe9467e5f2366cbe667662a694..f2975f7324b428d65c0b40f5466115b11393ecd6 100644
--- a/content/public/test/mock_render_process_host.cc
+++ b/content/public/test/mock_render_process_host.cc
@@ -12,6 +12,7 @@
 #include "content/browser/renderer_host/render_view_host_impl.h"
 #include "content/browser/renderer_host/render_widget_host_impl.h"
 #include "content/common/child_process_host_impl.h"
+#include "content/public/browser/browser_context.h"
 #include "content/public/browser/global_request_id.h"
 #include "content/public/browser/render_widget_host_iterator.h"
 #include "content/public/browser/storage_partition.h"
@@ -99,7 +100,7 @@ bool MockRenderProcessHost::IsIsolatedGuest() const {
 }
 
 StoragePartition* MockRenderProcessHost::GetStoragePartition() const {
-  return NULL;
+  return BrowserContext::GetDefaultStoragePartition(browser_context_);
 }
 
 void MockRenderProcessHost::AddWord(const base::string16& word) {