Speed up CBC_OneDimWriter::RenderResult().

Reserve space for all the appends to |CBC_OneDimWriter::m_output|.

BUG=chromium:925415

Change-Id: I5a944ba0ec74127270906ca432148df076855f6d
Reviewed-on: https://pdfium-review.googlesource.com/c/49110
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>

fxbarcode/oned/BC_OneDimWriter.cpp

diff --git a/fxbarcode/oned/BC_OneDimWriter.cpp b/fxbarcode/oned/BC_OneDimWriter.cpp
index 29fab7b..861f8d2 100644
--- a/fxbarcode/oned/BC_OneDimWriter.cpp
+++ b/fxbarcode/oned/BC_OneDimWriter.cpp
@@ -276,6 +276,7 @@
   m_barWidth = m_Width;
 
   m_output.clear();
+  m_output.reserve(codeOldLength * m_multiple);
   for (int32_t inputX = 0, outputX = leftPadding * m_multiple;
        inputX < codeOldLength; ++inputX, outputX += m_multiple) {
     if (code[inputX] != 1)