Don't copy ColumnMap in CSVPassword

CSVPassword represents a credential stored in one CSV line. For
parsing the CSV line, CSVPassword needs to understand the meaning of
columns, which it does through a ColumnMap -- a map from column
indices to column types. Currently, CSVPassword stores its own copy of
the map.

This map is the same for all lines in a single CSV blob. Sharing this
single map among all CSVPassword instances avoids many copies of the
map.

Therefore this CL changes CSVPassword to keep a reference to the map.

Bug: 934326
Change-Id: Id52e3db26fa1fd804f987103bf62e295102f2ce8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1698401
Commit-Queue: Vaclav Brozek <vabr@chromium.org>
Commit-Queue: Jan Wilken Dörrie <jdoerrie@chromium.org>
Auto-Submit: Vaclav Brozek <vabr@chromium.org>
Reviewed-by: Jan Wilken Dörrie <jdoerrie@chromium.org>
Cr-Commit-Position: refs/heads/master@{#681888}

components/password_manager/core/browser/import/csv_password.cc

@@ -17,8 +17,8 @@ namespace password_manager {
 
 using ::autofill::PasswordForm;
 
-CSVPassword::CSVPassword(ColumnMap map, base::StringPiece csv_row)
-    : map_(std::move(map)), row_(csv_row) {}
+CSVPassword::CSVPassword(const ColumnMap& map, base::StringPiece csv_row)
+    : map_(map), row_(csv_row) {}
 
 CSVPassword::~CSVPassword() = default;
 

components/password_manager/core/browser/import/csv_password.h

@@ -24,7 +24,7 @@ class CSVPassword {
   // Number of values in the Label enum.
   static constexpr size_t kLabelCount = 3;
 
-  CSVPassword(ColumnMap map, base::StringPiece csv_row);
+  CSVPassword(const ColumnMap& map, base::StringPiece csv_row);
   CSVPassword(const CSVPassword&) = delete;
   CSVPassword(CSVPassword&&) = delete;
   CSVPassword& operator=(const CSVPassword&) = delete;
@@ -45,7 +45,7 @@ class CSVPassword {
   // operator=().
 
   // |map_| stores the meaning of particular columns in the row.
-  ColumnMap map_;
+  const ColumnMap& map_;
   // |row_| contains the CSV row from which the PasswordForm is parsed.
   base::StringPiece row_;
 };