Add comments about ToFoo() functions to WTFString.h and AtomicString.h.

NOTRY=true

Bug: 746157
Change-Id: If1a8d3ecfa0101f6a8d432c658f676089830203c
Reviewed-on: https://chromium-review.googlesource.com/599270Reviewed-by: Takayoshi Kochi <kochi@chromium.org>
Commit-Queue: Kent Tamura <tkent@chromium.org>
Cr-Commit-Position: refs/heads/master@{#491648}

third_party/WebKit/Source/platform/wtf/text/AtomicString.h

@@ -185,6 +185,7 @@ class WTF_EXPORT AtomicString {
   AtomicString LowerASCII() const;
   AtomicString UpperASCII() const;
 
+  // See comments in WTFString.h.
   int ToInt(bool* ok = 0) const { return string_.ToInt(ok); }
   double ToDouble(bool* ok = 0) const { return string_.ToDouble(ok); }
   float ToFloat(bool* ok = 0) const { return string_.ToFloat(ok); }

third_party/WebKit/Source/platform/wtf/text/WTFString.h

@@ -373,12 +373,38 @@ class WTF_EXPORT String {
 
   // Convert the string into a number.
 
+  // The following ToFooStrict functions accept:
+  //  - leading '+'
+  //  - leading Unicode whitespace
+  //  - trailing Unicode whitespace
+  //  - no "-0" (ToUIntStrict and ToUInt64Strict)
+  //  - no out-of-range numbers which the resultant type can't represent
+  //
+  // If the input string is not acceptable, 0 is returned and |*ok| becomes
+  // |false|.
+  //
+  // We can use these functions to implement a Web Platform feature only if the
+  // input string is already valid according to the specification of the
+  // feature.
   int ToIntStrict(bool* ok = 0) const;
   unsigned ToUIntStrict(bool* ok = 0) const;
   unsigned HexToUIntStrict(bool* ok) const;
   int64_t ToInt64Strict(bool* ok = 0) const;
   uint64_t ToUInt64Strict(bool* ok = 0) const;
 
+  // The following ToFoo functions accept:
+  //  - leading '+'
+  //  - leading Unicode whitespace
+  //  - trailing garbage
+  //  - no "-0" (ToUInt and ToUInt64)
+  //  - no out-of-range numbers which the resultant type can't represent
+  //
+  // If the input string is not acceptable, 0 is returned and |*ok| becomes
+  // |false|.
+  //
+  // We can use these functions to implement a Web Platform feature only if the
+  // input string is already valid according to the specification of the
+  // feature.
   int ToInt(bool* ok = 0) const;
   unsigned ToUInt(bool* ok = 0) const;
   int64_t ToInt64(bool* ok = 0) const;
@@ -400,6 +426,13 @@ class WTF_EXPORT String {
   // A small absolute numbers which a double/float can't represent is accepted,
   // and 0 is returned
   //
+  // If the input string is not acceptable, 0.0 is returned and |*ok| becomes
+  // |false|.
+  //
+  // We can use these functions to implement a Web Platform feature only if the
+  // input string is already valid according to the specification of the
+  // feature.
+  //
   // FIXME: Like the strict functions above, these give false for "ok" when
   // there is trailing garbage.  Like the non-strict functions above, these
   // return the value when there is trailing garbage.  It would be better if