Adds unit tests for offline_pages::PrerenderAdapter calling PrerenderManager.

chrome/browser/android/offline_pages/prerender_adapter.cc

Index: chrome/browser/android/offline_pages/prerender_adapter.cc
diff --git a/chrome/browser/android/offline_pages/prerender_adapter.cc b/chrome/browser/android/offline_pages/prerender_adapter.cc
index 031314981274d1e0ad11ebb66c641c4fb6197515..6741f7295b62045e172451b7e70afee9b4304d53 100644
--- a/chrome/browser/android/offline_pages/prerender_adapter.cc
+++ b/chrome/browser/android/offline_pages/prerender_adapter.cc
@@ -17,7 +17,7 @@ PrerenderAdapter::Observer::Observer() {}
 PrerenderAdapter::Observer::~Observer() {}
 
 PrerenderAdapter::PrerenderAdapter(PrerenderAdapter::Observer* observer)
-    : observer_(observer) {
+    : observer_(observer), test_prerender_manager_(nullptr) {
   DCHECK(observer);
 }
 
@@ -41,6 +41,10 @@ bool PrerenderAdapter::StartPrerender(
   Profile* profile = Profile::FromBrowserContext(browser_context);
   prerender::PrerenderManager* manager =
       prerender::PrerenderManagerFactory::GetForProfile(profile);
+  if (test_prerender_manager_) {
+    DVLOG(1) << "Using test PrerenderManager";
+    manager = test_prerender_manager_;
+  }
   DCHECK(manager);
 
   // Start prerendering the url and capture the handle for the prerendering.
@@ -100,4 +104,9 @@ void PrerenderAdapter::OnPrerenderStop(prerender::PrerenderHandle* handle) {
   observer_->OnPrerenderStop();
 }
 
+void PrerenderAdapter::SetPrerenderManagerForTest(
+    prerender::PrerenderManager* test_prerender_manager) {
+  test_prerender_manager_ = test_prerender_manager;
+}
+
 }  // namespace offline_pages