validation: Use existing chainstate in ChainstateManager::ProcessNewBlockHeaders

[META] This commit should be followed up by removing the comments and
       assertions meant only to show that the change is correct.

Author: dongcarl

src/validation.cpp

@@ -3644,14 +3644,15 @@ bool BlockManager::AcceptBlockHeader(const CBlockHeader& block, BlockValidationS
 // Exposed wrapper for AcceptBlockHeader
 bool ChainstateManager::ProcessNewBlockHeaders(const std::vector<CBlockHeader>& headers, BlockValidationState& state, const CChainParams& chainparams, const CBlockIndex** ppindex)
 {
+    assert(std::addressof(::ChainstateActive()) == std::addressof(ActiveChainstate()));
     AssertLockNotHeld(cs_main);
     {
         LOCK(cs_main);
         for (const CBlockHeader& header : headers) {
             CBlockIndex *pindex = nullptr; // Use a temp pindex instead of ppindex to avoid a const_cast
             bool accepted = m_blockman.AcceptBlockHeader(
                 header, state, chainparams, &pindex);
-            ::ChainstateActive().CheckBlockIndex(chainparams.GetConsensus());
+            ActiveChainstate().CheckBlockIndex(chainparams.GetConsensus());
 
             if (!accepted) {
                 return false;
@@ -3661,8 +3662,8 @@ bool ChainstateManager::ProcessNewBlockHeaders(const std::vector<CBlockHeader>&
             }
         }
     }
-    if (NotifyHeaderTip(::ChainstateActive())) {
-        if (::ChainstateActive().IsInitialBlockDownload() && ppindex && *ppindex) {
+    if (NotifyHeaderTip(ActiveChainstate())) {
+        if (ActiveChainstate().IsInitialBlockDownload() && ppindex && *ppindex) {
             LogPrintf("Synchronizing blockheaders, height: %d (~%.2f%%)\n", (*ppindex)->nHeight, 100.0/((*ppindex)->nHeight+(GetAdjustedTime() - (*ppindex)->GetBlockTime()) / Params().GetConsensus().nPowTargetSpacing) * (*ppindex)->nHeight);
         }
     }