Do more validation in CPDF_Annot quad point methods.

CPDF_Annot::BoundingRectFromQuadPoints() and
CPDF_Annot::RectFromQuadPoints() should handle out of bound indices
gracefully, rather than hitting an ASSERT().

BUG=pdfium:1198

Change-Id: I548691dc4110ff509e94a9e961bd760fa10e505f
Reviewed-on: https://pdfium-review.googlesource.com/c/46412
Commit-Queue: Lei Zhang <thestig@chromium.org>
Reviewed-by: Tom Sepez <tsepez@chromium.org>

core/fpdfdoc/cpdf_annot.cpp

diff --git a/core/fpdfdoc/cpdf_annot.cpp b/core/fpdfdoc/cpdf_annot.cpp
index 39707b8..ee15879 100644
--- a/core/fpdfdoc/cpdf_annot.cpp
+++ b/core/fpdfdoc/cpdf_annot.cpp
@@ -234,11 +234,11 @@
     const CPDF_Dictionary* pAnnotDict) {
   CFX_FloatRect ret;
   const CPDF_Array* pArray = pAnnotDict->GetArrayFor("QuadPoints");
-  if (!pArray)
+  size_t nQuadPointCount = pArray ? QuadPointCount(pArray) : 0;
+  if (nQuadPointCount == 0)
     return ret;
 
   ret = RectFromQuadPointsArray(pArray, 0);
-  size_t nQuadPointCount = QuadPointCount(pArray);
   for (size_t i = 1; i < nQuadPointCount; ++i) {
     CFX_FloatRect rect = RectFromQuadPointsArray(pArray, i);
     ret.Union(rect);
@@ -250,7 +250,8 @@
 CFX_FloatRect CPDF_Annot::RectFromQuadPoints(const CPDF_Dictionary* pAnnotDict,
                                              size_t nIndex) {
   const CPDF_Array* pArray = pAnnotDict->GetArrayFor("QuadPoints");
-  if (!pArray)
+  size_t nQuadPointCount = pArray ? QuadPointCount(pArray) : 0;
+  if (nIndex >= nQuadPointCount)
     return CFX_FloatRect();
   return RectFromQuadPointsArray(pArray, nIndex);
 }

core/fpdfdoc/cpdf_annot_unittest.cpp

diff --git a/core/fpdfdoc/cpdf_annot_unittest.cpp b/core/fpdfdoc/cpdf_annot_unittest.cpp
index 287f034..40817f4 100644
--- a/core/fpdfdoc/cpdf_annot_unittest.cpp
+++ b/core/fpdfdoc/cpdf_annot_unittest.cpp
@@ -48,6 +48,13 @@
   EXPECT_EQ(0.0f, rect.right);
   EXPECT_EQ(0.0f, rect.top);
 
+  dict.SetFor("QuadPoints", CreateQuadPointArrayFromVector({0, 1, 2}));
+  rect = CPDF_Annot::BoundingRectFromQuadPoints(&dict);
+  EXPECT_EQ(0.0f, rect.left);
+  EXPECT_EQ(0.0f, rect.bottom);
+  EXPECT_EQ(0.0f, rect.right);
+  EXPECT_EQ(0.0f, rect.top);
+
   dict.SetFor("QuadPoints",
               CreateQuadPointArrayFromVector({0, 1, 2, 3, 4, 5, 6, 7}));
   rect = CPDF_Annot::BoundingRectFromQuadPoints(&dict);
@@ -86,6 +93,11 @@
   EXPECT_EQ(5.0f, rect.bottom);
   EXPECT_EQ(2.0f, rect.right);
   EXPECT_EQ(3.0f, rect.top);
+  rect = CPDF_Annot::RectFromQuadPoints(&dict, 5);
+  EXPECT_EQ(0.0f, rect.left);
+  EXPECT_EQ(0.0f, rect.bottom);
+  EXPECT_EQ(0.0f, rect.right);
+  EXPECT_EQ(0.0f, rect.top);
 
   dict.SetFor("QuadPoints", CreateQuadPointArrayFromVector(
                                 {0, 1, 2, 3, 4, 5, 6, 7, 8, 7, 6, 5,