Default to 1 when --force-device-scale-factor has an invalid value.

base/strings/string_number_conversions.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef BASE_STRINGS_STRING_NUMBER_CONVERSIONS_H_
 #define BASE_STRINGS_STRING_NUMBER_CONVERSIONS_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 46 matching lines @@
 //    by the data type.
 //  - Underflow. |*output| will be set to the minimum value supported
 //    by the data type.
 //  - Trailing characters in the string after parsing the number.  |*output|
 //    will be set to the value of the number that was parsed.
 //  - Leading whitespace in the string before parsing the number. |*output| will
 //    be set to the value of the number that was parsed.
 //  - No characters parseable as a number at the beginning of the string.
 //    |*output| will be set to 0.
 //  - Empty string.  |*output| will be set to 0.
+// WARNING: Will write to |output| even when returning false.
+//          Read the comments above carefully.
 BASE_EXPORT bool StringToInt(const StringPiece& input, int* output);
 BASE_EXPORT bool StringToInt(const StringPiece16& input, int* output);
 
 BASE_EXPORT bool StringToUint(const StringPiece& input, unsigned* output);
 BASE_EXPORT bool StringToUint(const StringPiece16& input, unsigned* output);
 
 BASE_EXPORT bool StringToInt64(const StringPiece& input, int64* output);
 BASE_EXPORT bool StringToInt64(const StringPiece16& input, int64* output);
 
 BASE_EXPORT bool StringToUint64(const StringPiece& input, uint64* output);
 BASE_EXPORT bool StringToUint64(const StringPiece16& input, uint64* output);
 
 BASE_EXPORT bool StringToSizeT(const StringPiece& input, size_t* output);
 BASE_EXPORT bool StringToSizeT(const StringPiece16& input, size_t* output);
 
 // For floating-point conversions, only conversions of input strings in decimal
 // form are defined to work.  Behavior with strings representing floating-point
-// numbers in hexadecimal, and strings representing non-fininte values (such as
+// numbers in hexadecimal, and strings representing non-finite values (such as
 // NaN and inf) is undefined.  Otherwise, these behave the same as the integral
 // variants.  This expects the input string to NOT be specific to the locale.
 // If your input is locale specific, use ICU to read the number.
+// WARNING: Will write to |output| even when returning false.
+//          Read the comments here and above StringToInt() carefully.
 BASE_EXPORT bool StringToDouble(const std::string& input, double* output);
 
 // Hex encoding ----------------------------------------------------------------
 
 // Returns a hex string representation of a binary buffer. The returned hex
 // string will be in upper case. This function does not check if |size| is
 // within reasonable limits since it's written with trusted data in mind.  If
 // you suspect that the data you want to format might be large, the absolute
 // max size for |size| should be is
 //   std::numeric_limits<size_t>::max() / 2
@@ skipping 24 matching lines @@
 // Similar to the previous functions, except that output is a vector of bytes.
 // |*output| will contain as many bytes as were successfully parsed prior to the
 // error.  There is no overflow, but input.size() must be evenly divisible by 2.
 // Leading 0x or +/- are not allowed.
 BASE_EXPORT bool HexStringToBytes(const std::string& input,
                                   std::vector<uint8>* output);
 
 }  // namespace base
 
 #endif  // BASE_STRINGS_STRING_NUMBER_CONVERSIONS_H_