Improve and simplify removal of unreachable code

src/hydrogen-mark-unreachable.h

Index: src/hydrogen-mark-unreachable.h
diff --git a/src/hydrogen-canonicalize.h b/src/hydrogen-mark-unreachable.h
similarity index 82%
copy from src/hydrogen-canonicalize.h
copy to src/hydrogen-mark-unreachable.h
index d2b289bc2124d2634c48a50b5c202c2941886b8c..e9459d5208c2963c1784330fccc43222ab620bed 100644
--- a/src/hydrogen-canonicalize.h
+++ b/src/hydrogen-mark-unreachable.h
@@ -25,8 +25,8 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-#ifndef V8_HYDROGEN_CANONICALIZE_H_
-#define V8_HYDROGEN_CANONICALIZE_H_
+#ifndef V8_HYDROGEN_MARK_UNREACHABLE_H_
+#define V8_HYDROGEN_MARK_UNREACHABLE_H_
 
 #include "hydrogen.h"
 
@@ -34,18 +34,20 @@ namespace v8 {
 namespace internal {
 
 
-class HCanonicalizePhase : public HPhase {
+class HMarkUnreachableBlocksPhase : public HPhase {
  public:
-  explicit HCanonicalizePhase(HGraph* graph)
-      : HPhase("H_Canonicalize", graph) { }
+  explicit HMarkUnreachableBlocksPhase(HGraph* graph)
+      : HPhase("H_Mark unrechable blocks", graph) { }
 
   void Run();
 
  private:
-  DISALLOW_COPY_AND_ASSIGN(HCanonicalizePhase);
+  void MarkUnreachableBlocks();
+
+  DISALLOW_COPY_AND_ASSIGN(HMarkUnreachableBlocksPhase);
 };
 
 
 } }  // namespace v8::internal
 
-#endif  // V8_HYDROGEN_CANONICALIZE_H_
+#endif  // V8_HYDROGEN_MARK_UNREACHABLE_H_