win: Implement exception snapshot

snapshot/exception_snapshot.h

Index: snapshot/exception_snapshot.h
diff --git a/snapshot/exception_snapshot.h b/snapshot/exception_snapshot.h
index f5ffd06a2295a9991a85143449c14d5ce4f77b04..9f68018ba80cee175535f97a6884d52a04bc1eb0 100644
--- a/snapshot/exception_snapshot.h
+++ b/snapshot/exception_snapshot.h
@@ -53,6 +53,9 @@ class ExceptionSnapshot {
   //! processed as `EXC_CRASH` when generated from another preceding exception:
   //! the original exception code will appear instead. The exception type as it
   //! was received will appear at index 0 of Codes().
+  //!
+  //! For Windows, this will be an \ref EXCEPTION_x "EXCEPTION_*" exception type
+  //! such as `EXCEPTION_ACCESS_VIOLATION`.
   virtual uint32_t Exception() const = 0;
 
   //! \brief Returns the second-level exception code identifying the exception.
@@ -69,6 +72,9 @@ class ExceptionSnapshot {
   //!
   //! In all cases on Mac OS X, the full exception code at index 0 as it was
   //! received will appear at index 1 of Codes().
+  //!
+  //! On Windows, this will either be 0 if the exception is continuable, or

[Mark Mentovai, 2015/08/18 17:52:13]

`0`

[scottmg, 2015/08/18 18:18:21]

Done.

+  //! `EXCEPTION_NONCONTINUABLE` to indicate a noncontinuable exception.
   virtual uint32_t ExceptionInfo() const = 0;
 
   //! \brief Returns the address that triggered the exception.
@@ -92,6 +98,10 @@ class ExceptionSnapshot {
   //! For Mac OS X, this will be a vector containing the original exception type
   //! and the values of `code[0]` and `code[1]` as received by a Mach exception
   //! handler.
+  //!
+  //! For Windows, these are additional arguments (if any) as provided to
+  //! `RaiseException()`. See the documentation for `ExceptionInformation` in
+  //! `EXCEPTION_RECORD`.

[Mark Mentovai, 2015/08/18 17:52:13]

Cool, thanks. You may want to add a little bit of Windows knowledge to our copy
of dbghelp.h now too, in the same way that you’ve done here.

[scottmg, 2015/08/18 18:18:20]

Done.

   virtual const std::vector<uint64_t>& Codes() const = 0;
 };