X87: [strong] Refactor ObjectStrength into a replacement for strong boolean args

port dd854449 (r28839)

original commit message:

    Boolean "is_strong" parameters have begun to proliferate across areas where
    strong mode semantics are different. This CL repurposes the existing
    ObjectStrength enum as a replacement for them.

BUG=
R=weiliang.lin@intel.com

Review URL: https://codereview.chromium.org/1173973002

Cr-Commit-Position: refs/heads/master@{#28952}

src/x87/lithium-x87.h

@@ -1182,7 +1182,7 @@ class LCmpT final : public LTemplateInstruction<1, 3, 0> {
   DECLARE_CONCRETE_INSTRUCTION(CmpT, "cmp-t")
   DECLARE_HYDROGEN_ACCESSOR(CompareGeneric)
 
-  LanguageMode language_mode() { return hydrogen()->language_mode(); }
+  Strength strength() { return hydrogen()->strength(); }
 
   LOperand* context() { return inputs_[0]; }
   Token::Value op() const { return hydrogen()->token(); }
@@ -1549,7 +1549,7 @@ class LArithmeticT final : public LTemplateInstruction<1, 3, 0> {
 
   DECLARE_HYDROGEN_ACCESSOR(BinaryOperation)
 
-  LanguageMode language_mode() { return hydrogen()->language_mode(); }
+  Strength strength() { return hydrogen()->strength(); }
 
  private:
   Token::Value op_;