Add assembler test.

src/mips/assembler-mips.h

Index: src/mips/assembler-mips.h
diff --git a/src/mips/assembler-mips.h b/src/mips/assembler-mips.h
index 17ba78979e042a0feaec16b701717d698897b2a6..fbeed471610211a67091e50244f73b5881314c7e 100644
--- a/src/mips/assembler-mips.h
+++ b/src/mips/assembler-mips.h
@@ -751,6 +751,8 @@ class Assembler : public AssemblerBase {
   void rotr(Register rd, Register rt, uint16_t sa);
   void rotrv(Register rd, Register rt, Register rs);
 
+  // Address computing instructions with shift.
+  void lsa(Register rd, Register rt, Register rs, uint8_t sa);
 
   // ------------Memory-instructions-------------