Fix backspace on 1st character of a line erases the line break.

Bug: chromium:836361
Change-Id: I39a0a3f9cb59ceb81f944dd5d0d4fd38a2e18a6b
Reviewed-on: https://pdfium-review.googlesource.com/31411
Reviewed-by: Ryan Harrison <rharrison@chromium.org>
Commit-Queue: Henrique Nakashima <hnakashima@chromium.org>

2 files changed, 317 insertions, 0 deletions

diff --git a/testing/resources/xfa/xfa_multiline_textfield.in b/testing/resources/xfa/xfa_multiline_textfield.in
new file mode 100644
index 0000000000..215bc28015
--- /dev/null
+++ b/testing/resources/xfa/xfa_multiline_textfield.in
@@ -0,0 +1,73 @@
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+
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+{{object 1 0}}
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+  /Extensions <<
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+  /Type /Catalog
+>>
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+    </pageSet>
+    <subform w="576pt" h="756pt" name="Page1">
+      <field name="TextField1" y="0pt" x="0pt" w="425pt" h="80pt">
+        <ui>
+          <textEdit multiLine="1">
+            <font typeface="Helvetica" size="16pt"/>
+          </textEdit>
+        </ui>
+      </field>
+    </subform>
+  </subform>
+</template>
+endstream
+endobj
+
+{{xfalocale 6 0}}
+
+{{xfapostamble 7 0}}
+
+{{xref}}
+{{trailer}}
+{{startxref}}
+%%EOF
diff --git a/testing/resources/xfa/xfa_multiline_textfield.pdf b/testing/resources/xfa/xfa_multiline_textfield.pdf
new file mode 100644
index 0000000000..f88af5bf9a
--- /dev/null
+++ b/testing/resources/xfa/xfa_multiline_textfield.pdf
@@ -0,0 +1,244 @@
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+% ò¤ô
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+  /Type /Catalog
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+
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+stream
+<config xmlns="http://www.xfa.org/schema/xci/3.0/">
+  <agent name="designer">
+    <destination>pdf</destination>
+    <pdf>
+      <fontInfo/>
+    </pdf>
+  </agent>
+  <present>
+    <pdf>
+      <version>1.7</version>
+      <adobeExtensionLevel>8</adobeExtensionLevel>
+      <renderPolicy>client</renderPolicy>
+      <scriptModel>XFA</scriptModel>
+      <interactive>1</interactive>
+    </pdf>
+    <xdp>
+      <packets>*</packets>
+    </xdp>
+    <destination>pdf</destination>
+    <script>
+      <runScripts>server</runScripts>
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+  </present>
+  <acrobat>
+    <acrobat7>
+      <dynamicRender>required</dynamicRender>
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+    <validate>preSubmit</validate>
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+  <locale name="en_US" desc="English (United States)">
+    <calendarSymbols name="gregorian">
+      <monthNames>
+        <month>January</month>
+        <month>February</month>
+        <month>March</month>
+        <month>April</month>
+        <month>May</month>
+        <month>June</month>
+        <month>July</month>
+        <month>August</month>
+        <month>September</month>
+        <month>October</month>
+        <month>November</month>
+        <month>December</month>
+      </monthNames>
+      <monthNames abbr="1">
+        <month>Jan</month>
+        <month>Feb</month>
+        <month>Mar</month>
+        <month>Apr</month>
+        <month>May</month>
+        <month>Jun</month>
+        <month>Jul</month>
+        <month>Aug</month>
+        <month>Sep</month>
+        <month>Oct</month>
+        <month>Nov</month>
+        <month>Dec</month>
+      </monthNames>
+      <dayNames>
+        <day>Sunday</day>
+        <day>Monday</day>
+        <day>Tuesday</day>
+        <day>Wednesday</day>
+        <day>Thursday</day>
+        <day>Friday</day>
+        <day>Saturday</day>
+      </dayNames>
+      <dayNames abbr="1">
+        <day>Sun</day>
+        <day>Mon</day>
+        <day>Tue</day>
+        <day>Wed</day>
+        <day>Thu</day>
+        <day>Fri</day>
+        <day>Sat</day>
+      </dayNames>
+      <meridiemNames>
+        <meridiem>AM</meridiem>
+        <meridiem>PM</meridiem>
+      </meridiemNames>
+      <eraNames>
+        <era>BC</era>
+        <era>AD</era>
+      </eraNames>
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+      <datePattern name="long">MMMM D, YYYY</datePattern>
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+      <timePattern name="short">h:MM A</timePattern>
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+      <numberSymbol name="percent">%</numberSymbol>
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+    <currencySymbols>
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