BackForwardCache: Remove content::IsInBackForwardCache

Use RenderFrameHost::IsInBackForwardCache, which was introduced by
https://chromium-review.googlesource.com/c/chromium/src/+/2073980
instead.

Bug: 1001087
Change-Id: I715eabc805610c6eff8b801ec9a60419582b7c24
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2091325
Commit-Queue: Hajime Hoshi <hajimehoshi@chromium.org>
Reviewed-by: Alex Moshchuk <alexmos@chromium.org>
Reviewed-by: Alexander Timin <altimin@chromium.org>
Reviewed-by: Jan Wilken Dörrie <jdoerrie@chromium.org>
Cr-Commit-Position: refs/heads/master@{#756608}

chrome/browser/password_manager/password_manager_browsertest.cc

@@ -4004,7 +4004,7 @@ IN_PROC_BROWSER_TEST_F(PasswordManagerBackForwardCacheBrowserTest,
   EXPECT_TRUE(NavigateToURL(
       WebContents(), embedded_test_server()->GetURL("a.com", "/title1.html")));
   EXPECT_FALSE(rfh_deleted_observer.deleted());
-  EXPECT_TRUE(content::IsInBackForwardCache(rfh));
+  EXPECT_TRUE(rfh->IsInBackForwardCache());
 
   // Restore the cached page.
   WebContents()->GetController().GoBack();
@@ -4060,7 +4060,7 @@ IN_PROC_BROWSER_TEST_F(PasswordManagerBackForwardCacheBrowserTest,
   // Navigate away.
   EXPECT_TRUE(NavigateToURL(
       WebContents(), embedded_test_server()->GetURL("b.com", "/title1.html")));
-  EXPECT_TRUE(content::IsInBackForwardCache(rfh));
+  EXPECT_TRUE(rfh->IsInBackForwardCache());
 
   // Restore the cached page.
   WebContents()->GetController().GoBack();

content/public/test/back_forward_cache_util.cc

@@ -13,10 +13,6 @@
 
 namespace content {
 
-bool IsInBackForwardCache(RenderFrameHost* render_frame_host) {
-  return render_frame_host->IsInBackForwardCache();
-}
-
 class BackForwardCacheDisabledTester::Impl
     : public BackForwardCacheTestDelegate {
  public:

content/public/test/back_forward_cache_util.h

@@ -9,14 +9,6 @@
 
 namespace content {
 class BackForwardCacheImpl;
-class RenderFrameHost;
-
-// Returns true if |render_frame_host| is currently stored in the
-// BackForwardCache.
-//
-// TODO(hajimehoshi): This function is no longer needed. Remove this.
-bool IsInBackForwardCache(RenderFrameHost* render_frame_host)
-    WARN_UNUSED_RESULT;
 
 // This is a helper class to check in the tests that back-forward cache
 // was disabled for a particular reason.