[turbofan] Moved split edge form validation lower.

There are multiple ways we may construct an instruction sequence.
Moved the split edge form validation where they must all eventually
chokepoint to - the register allocation pipeline, which is also the main
and first consumer of this property.

BUG=

Review URL: https://codereview.chromium.org/1810293003

Cr-Commit-Position: refs/heads/master@{#34903}

src/compiler/instruction.cc

@@ -682,10 +682,6 @@ InstructionSequence::InstructionSequence(Isolate* isolate,
       representations_(zone()),
       deoptimization_entries_(zone()) {
   block_starts_.reserve(instruction_blocks_->size());
-
-#if DEBUG
-  ValidateEdgeSplitForm();
-#endif
 }
 
 

src/compiler/pipeline.cc

@@ -1445,6 +1445,7 @@ void Pipeline::AllocateRegisters(const RegisterConfiguration* config,
   base::SmartArrayPointer<char> debug_name;
 #ifdef DEBUG
   debug_name = info()->GetDebugName();
+  data_->sequence()->ValidateEdgeSplitForm();
 #endif
 
   data->InitializeRegisterAllocationData(config, descriptor, debug_name.get());