Show alt text when source image is missing or broken or not found.

LayoutTests/TestExpectations

Index: LayoutTests/TestExpectations
diff --git a/LayoutTests/TestExpectations b/LayoutTests/TestExpectations
index 0c9765f34fd3bb55bccad7d6a8fbc3939870dd5d..ff8429312e9446a365db682f57e1f48d28cf8deb 100644
--- a/LayoutTests/TestExpectations
+++ b/LayoutTests/TestExpectations
@@ -1321,3 +1321,21 @@ crbug.com/357462 http/tests/security/contentSecurityPolicy/1.1/frame-ancestors/f
 # After libwebp-0.4.1 lands in Chrome these need to be rebaselined.
 crbug.com/374343 fast/canvas/canvas-toDataURL-webp.html [ Skip ]
 crbug.com/374343 virtual/gpu/fast/canvas/canvas-toDataURL-webp.html [ Skip ]
+
+#alt Text layout tests rebaseline
+crbug.com/157207 crbug.com/773 editing/selection/select-missing-image.html [ NeedsRebaseline ]
+crbug.com/157207 crbug.com/773 fast/block/float/002.html [ NeedsRebaseline ]
+crbug.com/157207 crbug.com/773 fast/block/float/015.html [ NeedsRebaseline ]
+crbug.com/157207 crbug.com/773 fast/block/positioning/061.html [ NeedsRebaseline ]
+crbug.com/157207 crbug.com/773 fast/encoding/utf-16-big-endian.html [ NeedsRebaseline ]
+crbug.com/157207 crbug.com/773 fast/encoding/utf-16-little-endian.html [ NeedsRebaseline ]
+crbug.com/157207 crbug.com/773 fast/forms/002.html [ NeedsRebaseline ]
+crbug.com/157207 crbug.com/773 fast/forms/005.html [ NeedsRebaseline ]
+crbug.com/157207 crbug.com/773 fast/lists/inlineBoxWrapperNullCheck.html [ NeedsRebaseline ]
+crbug.com/157207 crbug.com/773 fast/text/bidi-img-alt-text.html [ NeedsRebaseline ]
+crbug.com/157207 crbug.com/773 fast/text/whitespace/normal-after-nowrap-breaking.html   [ NeedsRebaseline ]
+crbug.com/157207 crbug.com/773 tables/mozilla/bugs/bug2997.html [ NeedsRebaseline ]
+crbug.com/157207 crbug.com/773 tables/mozilla/bugs/bug4527.html [ NeedsRebaseline ]
+crbug.com/157207 crbug.com/773 tables/mozilla/collapsing_borders/bug41262-3.html [ NeedsRebaseline ]
+crbug.com/157207 crbug.com/773 [ Mac Win ] virtual/antialiasedtext/fast/text/bidi-img-alt-text.html [ NeedsRebaseline ]
+crbug.com/157207 crbug.com/773 [ Mac Win ] virtual/antialiasedtext/fast/text/whitespace/normal-after-nowrap-breaking.html [ NeedsRebaseline ]