PDF: Fix extra NUL characters from incorrect WriteInto() calls.

pdf/pdfium/pdfium_engine.cc

Index: pdf/pdfium/pdfium_engine.cc
diff --git a/pdf/pdfium/pdfium_engine.cc b/pdf/pdfium/pdfium_engine.cc
index 8c49b9dc0bc67a56ed1bb3732a394ae62ec88ccb..7dca0136ade50b11956dd198c95a1ba895eddea3 100644
--- a/pdf/pdfium/pdfium_engine.cc
+++ b/pdf/pdfium/pdfium_engine.cc
@@ -2050,12 +2050,18 @@ void PDFiumEngine::SearchUsingICU(const base::string16& term,
   }
   if (text_length <= 0)
     return;
+
   unsigned short* data =
       reinterpret_cast<unsigned short*>(WriteInto(&page_text, text_length + 1));
-  FPDFText_GetText(pages_[current_page]->GetTextPage(),
-                   character_to_start_searching_from,
-                   text_length,
-                   data);
+  int written = FPDFText_GetText(pages_[current_page]->GetTextPage(),
+                                 character_to_start_searching_from,
+                                 text_length,
+                                 data);
+  if (written < 1)
+    page_text.resize(0);
+  else
+    page_text.resize(written - 1);
+
   std::vector<PDFEngine::Client::SearchStringResult> results;
   client_->SearchString(
       page_text.c_str(), term.c_str(), case_sensitive, &results);