[turbofan] Remove dead {is_liveness_analysis_enabled}.

R=jarin@chromium.org

Review-Url: https://codereview.chromium.org/2655533003
Cr-Commit-Position: refs/heads/master@{#42693}

src/compiler/bytecode-graph-builder.cc

@@ -470,7 +470,6 @@ BytecodeGraphBuilder::BytecodeGraphBuilder(
       input_buffer_size_(0),
       input_buffer_(nullptr),
       exit_controls_(local_zone),
-      is_liveness_analysis_enabled_(FLAG_analyze_environment_liveness),
       state_values_cache_(jsgraph),
       source_positions_(source_positions),
       start_position_(shared_info->start_position(), inlining_id) {}

src/compiler/bytecode-graph-builder.h

@@ -261,10 +261,6 @@ class BytecodeGraphBuilder {
     bytecode_analysis_ = bytecode_analysis;
   }
 
-  bool IsLivenessAnalysisEnabled() const {
-    return this->is_liveness_analysis_enabled_;
-  }
-
 #define DECLARE_VISIT_BYTECODE(name, ...) void Visit##name();
   BYTECODE_LIST(DECLARE_VISIT_BYTECODE)
 #undef DECLARE_VISIT_BYTECODE
@@ -303,8 +299,6 @@ class BytecodeGraphBuilder {
   // Control nodes that exit the function body.
   ZoneVector<Node*> exit_controls_;
 
-  bool const is_liveness_analysis_enabled_;
-
   StateValuesCache state_values_cache_;
 
   // The source position table, to be populated.