Fix SharedSampler to cope correctly with zero-thread processes.

chrome/browser/task_manager/sampling/shared_sampler_win.cc

Index: chrome/browser/task_manager/sampling/shared_sampler_win.cc
diff --git a/chrome/browser/task_manager/sampling/shared_sampler_win.cc b/chrome/browser/task_manager/sampling/shared_sampler_win.cc
index 4cd06e986356e47e9d70536d15eb17bc3df8475d..402ebc7c6d5fd3d771ff99140bcbcbb7a8da789f 100644
--- a/chrome/browser/task_manager/sampling/shared_sampler_win.cc
+++ b/chrome/browser/task_manager/sampling/shared_sampler_win.cc
@@ -457,10 +457,12 @@ std::unique_ptr<ProcessDataSnapshot> SharedSampler::CaptureSnapshot() {
     // the buffer boundary.
     if (offset + sizeof(SYSTEM_PROCESS_INFORMATION) > data_buffer.size())
       break;
-    if (offset + sizeof(SYSTEM_PROCESS_INFORMATION) +
-            (pi->NumberOfThreads - 1) * sizeof(SYSTEM_THREAD_INFORMATION) >
-      data_buffer.size())
+    if (pi->NumberOfThreads >= 0 &&

[stanisc, 2016/12/13 17:12:20]

This is to prevent underflow when subtracting 1, right? Should this be > 0?

[Wez, 2016/12/13 21:30:48]

*facepalm* Beware late-night coding - fixed!

Best of all, Clang actually caught this as a tautologous check (since
NumberOfThreads is unsigned). :D

+        (offset + sizeof(SYSTEM_PROCESS_INFORMATION) +
+             (pi->NumberOfThreads - 1) * sizeof(SYSTEM_THREAD_INFORMATION) >
+         data_buffer.size())) {
       break;
+    }
 
     if (pi->ImageName.Buffer) {
       // Validate that the image name is within the buffer boundary.