Add format width and precision tests.

core/src/fxcrt/fx_basic_bstring_unittest.cpp

Index: core/src/fxcrt/fx_basic_bstring_unittest.cpp
diff --git a/core/src/fxcrt/fx_basic_bstring_unittest.cpp b/core/src/fxcrt/fx_basic_bstring_unittest.cpp
index 3779397891182a8ae30b177e1cc7d66439b748d3..79d88733194c15d08ae39209af602cfc634663e4 100644
--- a/core/src/fxcrt/fx_basic_bstring_unittest.cpp
+++ b/core/src/fxcrt/fx_basic_bstring_unittest.cpp
@@ -603,3 +603,31 @@ TEST(fxcrt, ByteStringCOperatorNE) {
   EXPECT_TRUE(c_string2 != byte_string_c);
   EXPECT_TRUE(c_string3 != byte_string_c);
 }
+
+TEST(fxcrt, ByteStringFormatWidth) {
+  {
+    CFX_ByteString str;

[Tom Sepez, 2015/11/03 17:19:49]

Do these support the %*d syntax as well?  If so, can we test that.
Also, what happens if we put in a negative value or 0 value, eg
%-1d or %0d?

[dsinclair, 2015/11/03 18:50:08]

Done.

+    str.Format("%5d", 1);
+    EXPECT_EQ("    1", str);
+  }
+
+  {
+    CFX_ByteString str;
+    str.Format("%d", 1);
+    EXPECT_EQ("1", str);
+  }
+}
+
+TEST(fxcrt, ByteStringFormatPrecision) {
+  {
+    CFX_ByteString str;
+    str.Format("%.2f", 1.12345);
+    EXPECT_EQ("1.12", str);
+  }
+
+  {
+    CFX_ByteString str;
+    str.Format("%f", 1.12345);
+    EXPECT_EQ("1.123450", str);
+  }
+}