Add some string helper classes.

*re-land with build fix for Clang*

These helper functions mirror some utilities in Chrome, for splitting
strings along whitespace, or reading file contents into a string.

Also remove the hack for skipping the doubly-defined GLX header.

BUG=angleproject:892,angleproject:998

Change-Id: Ife43fbf5035a3be7820460bea1b26d0e632a4fb0
Reviewed-on: https://chromium-review.googlesource.com/272518
Tested-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
diff --git a/src/common/string_utils.cpp b/src/common/string_utils.cpp
new file mode 100644
index 0000000..171c501
--- /dev/null
+++ b/src/common/string_utils.cpp
@@ -0,0 +1,83 @@
+//
+// Copyright 2015 The ANGLE Project Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+//
+// string_utils:
+//   String helper functions.
+//
+
+#include "string_utils.h"
+
+#include <fstream>
+#include <sstream>
+
+namespace angle
+{
+
+void SplitString(const std::string &input,
+                 char delimiter,
+                 std::vector<std::string> *tokensOut)
+{
+    std::istringstream stream(input);
+    std::string token;
+
+    while (std::getline(stream, token, delimiter))
+    {
+        if (!token.empty())
+        {
+            tokensOut->push_back(token);
+        }
+    }
+}
+
+void SplitStringAlongWhitespace(const std::string &input,
+                                std::vector<std::string> *tokensOut)
+{
+    const char *delimiters = " \f\n\r\t\v";
+
+    std::istringstream stream(input);
+    std::string line;
+
+    while (std::getline(stream, line))
+    {
+        size_t prev = 0, pos;
+        while ((pos = line.find_first_of(delimiters, prev)) != std::string::npos)
+        {
+            if (pos > prev)
+                tokensOut->push_back(line.substr(prev, pos - prev));
+            prev = pos + 1;
+        }
+        if (prev < line.length())
+            tokensOut->push_back(line.substr(prev, std::string::npos));
+    }
+}
+
+bool HexStringToUInt(const std::string &input, unsigned int *uintOut)
+{
+    // Simple validity check
+    if (input[0] != '0' || input[1] != 'x' ||
+        input.find_first_not_of("0123456789ABCDEFabcdef", 2) != std::string::npos)
+    {
+        return false;
+    }
+
+    std::stringstream inStream(input);
+    inStream >> std::hex >> *uintOut;
+    return !inStream.fail();
+}
+
+bool ReadFileToString(const std::string &path, std::string *stringOut)
+{
+    std::ifstream inFile(path.c_str());
+    std::string str;
+
+    inFile.seekg(0, std::ios::end);
+    str.reserve(inFile.tellg());
+    inFile.seekg(0, std::ios::beg);
+
+    str.assign(std::istreambuf_iterator<char>(inFile), std::istreambuf_iterator<char>());
+    return !inFile.fail();
+}
+
+}