Fix a line trim to use the correct offset

We were previously trimming the string with the wrong prefix, which
meant that querying the Cpu brand from /proc/cpuinfo could be wrong if
the string matched "Processor\t: ".  We would use "model name\t: "
length to trim instead of the correct "Processor\t: " length.

BUG=788934

Change-Id: I1cc99e6c64ca89b25f53c51624db40cdafe24a6b
Reviewed-on: https://chromium-review.googlesource.com/791998Reviewed-by: Tommy Nyquist <nyquist@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: David Trainor <dtrainor@chromium.org>
Cr-Commit-Position: refs/heads/master@{#519802}

base/cpu.cc

@@ -114,10 +114,10 @@ std::string* CpuInfoBrand() {
     std::istringstream iss(contents);
     std::string line;
     while (std::getline(iss, line)) {
-      if ((line.compare(0, strlen(kModelNamePrefix), kModelNamePrefix) == 0 ||
-           line.compare(0, strlen(kProcessorPrefix), kProcessorPrefix) == 0)) {
+      if (line.compare(0, strlen(kModelNamePrefix), kModelNamePrefix) == 0)
         return new std::string(line.substr(strlen(kModelNamePrefix)));
-      }
+      if (line.compare(0, strlen(kProcessorPrefix), kProcessorPrefix) == 0)
+        return new std::string(line.substr(strlen(kProcessorPrefix)));
     }
 
     return new std::string();