ART: Fix off-by-two whitespace

Follow-up to change 134380. Fix the whitespace to be printed. Fix
style. It's surprising the linter did not complain.

Change-Id: I3abcde3f401fa1fd4d7a847ff1f071fba23ce6a7
diff --git a/runtime/dex_instruction.cc b/runtime/dex_instruction.cc
index 92e0f07..69fe874 100644
--- a/runtime/dex_instruction.cc
+++ b/runtime/dex_instruction.cc
@@ -142,11 +142,11 @@
   std::ostringstream os;
   const uint16_t* insn = reinterpret_cast<const uint16_t*>(this);
   for (size_t i = 0; i < inst_length; i++) {
-    os << StringPrintf("%02x%02x", (uint8_t)(insn[i] & 0x00FF),
-                       (uint8_t)((insn[i] & 0xFF00)>>8)) << " ";
+    os << StringPrintf("%02x%02x", static_cast<uint8_t>(insn[i] & 0x00FF),
+                       static_cast<uint8_t>((insn[i] & 0xFF00) >> 8)) << " ";
   }
   for (size_t i = inst_length; i < instr_code_units; i++) {
-    os << "       ";
+    os << "     ";
   }
   return os.str();
 }