Resolve all but two VC++ build warnings in pdfium.

core/src/fpdftext/fpdf_text_int.cpp

Index: core/src/fpdftext/fpdf_text_int.cpp
diff --git a/core/src/fpdftext/fpdf_text_int.cpp b/core/src/fpdftext/fpdf_text_int.cpp
index c9cfbdda2d4f29deaea92e8da7e69c10a45d8bbf..70178a54b0a875086bcc3578f7cd4412e0c870f5 100644
--- a/core/src/fpdftext/fpdf_text_int.cpp
+++ b/core/src/fpdftext/fpdf_text_int.cpp
@@ -37,13 +37,13 @@ FX_BOOL _IsIgnoreSpaceCharacter(FX_WCHAR curChar)
 FX_FLOAT _NormalizeThreshold(FX_FLOAT threshold)
 {
     if (threshold < 300) {
-        return threshold / 2.0;
+        return threshold / 2.0f;
     } else if (threshold < 500) {
-        return threshold / 4.0;
+        return threshold / 4.0f;
     } else if (threshold < 700) {
-        return threshold / 5.0;
+        return threshold / 5.0f;
     }
-    return threshold / 6.0;
+    return threshold / 6.0f;
 }
 
 FX_FLOAT _CalculateBaseSpace(const CPDF_TextObject* pTextObj,