fix certain progressive jpegs

Currently, when loading half scans of certain type of progressive jpegs, the last
scan is not displayed correctly. We provide a fix and a test.

Bug: 1156120
Change-Id: If6ab87bda49fddf28bdf2062fc155ac85f9290c8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2577498
Commit-Queue: Moritz Firsching <firsching@google.com>
Reviewed-by: Leon Scroggins <scroggo@google.com>
Auto-Submit: Moritz Firsching <firsching@google.com>
Cr-Commit-Position: refs/heads/master@{#835634}

third_party/blink/renderer/platform/image-decoders/jpeg/jpeg_image_decoder.cc

@@ -809,29 +809,36 @@ class JPEGImageReader final {
 
       case JPEG_DECOMPRESS_PROGRESSIVE:
         if (state_ == JPEG_DECOMPRESS_PROGRESSIVE) {
+          auto all_components_seen = [](const jpeg_decompress_struct& info) {
+            if (info.coef_bits) {
+              for (int c = 0; c < info.num_components; ++c) {
+                if (info.coef_bits[c][0] == -1) {
+                  // Haven't seen this component yet.
+                  return false;
+                }
+              }
+            }
+            return true;
+          };
           int status = 0;
+          int first_scan_to_display =
+              all_components_seen(info_) ? info_.input_scan_number : 0;
           do {
             decoder_error_mgr* err =
                 reinterpret_cast_ptr<decoder_error_mgr*>(info_.err);
             if (err->num_corrupt_warnings)
               break;
             status = jpeg_consume_input(&info_);
-          } while ((status != JPEG_SUSPENDED) && (status != JPEG_REACHED_EOI));
-
-          bool all_components_seen = true;
-          if (info_.coef_bits) {
-            for (int c = 0; c < info_.num_components; ++c) {
-              bool current_component_seen = info_.coef_bits[c][0] != -1;
-              all_components_seen &= current_component_seen;
-            }
-          }
-
-          int first_scan_to_display = 0;
-          if (!first_scan_to_display && all_components_seen) {
+            if (status == JPEG_REACHED_SOS || status == JPEG_REACHED_EOI ||
+                status == JPEG_SUSPENDED) {
+              // record the first scan where all components are present
+              if (!first_scan_to_display && all_components_seen(info_)) {
                 first_scan_to_display = info_.input_scan_number;
               }
+            }
+          } while (!(status == JPEG_SUSPENDED || status == JPEG_REACHED_EOI));
 
-          if (!all_components_seen) {
+          if (!first_scan_to_display) {
             return false;  // I/O suspension
           }
 

third_party/blink/web_tests/images/jpeg-with-half_scan-2.html

+<img src="resources/half_scan-2.jpg">

third_party/blink/web_tests/images/jpeg-with-half_scan.html

+<img src="resources/half_scan.jpg">