Bug 187265

Test imported/w3c/web-platform-tests/FileAPI/reading-data-section/filereader_abort.html crashes frequently on iOS Simulator Debug Wk2

Flakiness Dashboard:
https://webkit-test-results.webkit.org/dashboards/flakiness_dashboard.html#showAllRuns=true&tests=imported%2Fw3c%2Fweb-platform-tests%2FFileAPI%2Freading-data-section%2Ffilereader_abort.html

Curiously enough the crash log reports CRASHING TEST as "imported/mozilla/svg/smil/style/anim-css-fontsize-1-from-to-px-px-expected.svg"

Sample CrashLog:
https://build.webkit.org/results/Apple%20iOS%2011%20Simulator%20Debug%20WK2%20(Tests)/r233426%20(5169)/imported/w3c/web-platform-tests/FileAPI/reading-data-section/filereader_abort-crash-log.txt

Process:               com.apple.WebKit.WebContent.Development [4229]
Path:                  /Volumes/VOLUME/*/WebKit.framework/XPCServices/com.apple.WebKit.WebContent.xpc/com.apple.WebKit.WebContent.Development
Identifier:            com.apple.WebKit.WebContent.Development
Version:               606+ (606.1.20+)
Code Type:             X86-64 (Native)
Parent Process:        launchd_sim [96672]
Responsible:           com.apple.WebKit.WebContent.Development [4229]
User ID:               501

Date/Time:             2018-07-02 11:25:31.940 -0700
OS Version:            Mac OS X 10.13.4 (17E202)
Report Version:        12
Anonymous UUID:        628480A6-E7E2-AA80-1638-0BF1D7734AC5


Time Awake Since Boot: 5800000 seconds

System Integrity Protection: disabled

Crashed Thread:        0  Dispatch queue: com.apple.main-thread

Exception Type:        EXC_BAD_ACCESS (SIGSEGV)
Exception Codes:       KERN_INVALID_ADDRESS at 0x00000000bbadbeef
Exception Note:        EXC_CORPSE_NOTIFY

Termination Signal:    Segmentation fault: 11
Termination Reason:    Namespace SIGNAL, Code 0xb
Terminating Process:   exc handler [0]

VM Regions Near 0xbbadbeef:
--> 
    __TEXT                 000000010db74000-000000010db77000 [   12K] r-x/rwx SM=COW  /Volumes/VOLUME/*/WebKit.framework/XPCServices/com.apple.WebKit.WebContent.xpc/com.apple.WebKit.WebContent.Development

Application Specific Information:
CRASHING TEST: imported/mozilla/svg/smil/style/anim-css-fontsize-1-from-to-px-px-expected.svg
CoreSimulator 518.19 - Device: Managed 4 - Runtime: iOS 11.3 (15E217) - DeviceType: iPhone 5s

Thread 0 Crashed:: Dispatch queue: com.apple.main-thread
0   JavaScriptCore                	0x000000011bc71080 WTFCrash + 16 (Assertions.cpp:267)
1   com.apple.WebCore             	0x00000001214712f0 WebCore::FileReader::abort()::$_8::operator()(WebCore::ScriptExecutionContext&) const + 80 (FileReader.cpp:157)
2   com.apple.WebCore             	0x0000000121471274 WTF::Function<void (WebCore::ScriptExecutionContext&)>::CallableWrapper<WebCore::FileReader::abort()::$_8>::call(WebCore::ScriptExecutionContext&) + 52 (Function.h:101)
3   com.apple.WebCore             	0x0000000120b769ce WTF::Function<void (WebCore::ScriptExecutionContext&)>::operator()(WebCore::ScriptExecutionContext&) const + 158 (Function.h:56)
4   com.apple.WebCore             	0x0000000120b643dd WebCore::ScriptExecutionContext::Task::performTask(WebCore::ScriptExecutionContext&) + 29 (ScriptExecutionContext.h:188)
5   com.apple.WebCore             	0x0000000121201796 WebCore::Document::postTask(WebCore::ScriptExecutionContext::Task&&)::$_3::operator()() + 278 (Document.cpp:5853)
6   com.apple.WebCore             	0x00000001212015d9 WTF::Function<void ()>::CallableWrapper<WebCore::Document::postTask(WebCore::ScriptExecutionContext::Task&&)::$_3>::call() + 25 (Function.h:101)
7   JavaScriptCore                	0x000000011bc961cb WTF::Function<void ()>::operator()() const + 139 (Function.h:56)
8   JavaScriptCore                	0x000000011bcc11ab WTF::dispatchFunctionsFromMainThread() + 331 (MainThread.cpp:129)
9   JavaScriptCore                	0x000000011bcc3db5 -[JSWTFMainThreadCaller call] + 21 (MainThreadMac.mm:55)
10  com.apple.Foundation          	0x000000010dc66d5e __NSThreadPerformPerform + 330
11  com.apple.CoreFoundation      	0x0000000113214bb1 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 17
12  com.apple.CoreFoundation      	0x00000001131f94af __CFRunLoopDoSources0 + 271
13  com.apple.CoreFoundation      	0x00000001131f8a6f __CFRunLoopRun + 1263
14  com.apple.CoreFoundation      	0x00000001131f830b CFRunLoopRunSpecific + 635
15  com.apple.Foundation          	0x000000010dc21b4a -[NSRunLoop(NSRunLoop) runMode:beforeDate:] + 274
16  com.apple.Foundation          	0x000000010dc21a25 -[NSRunLoop(NSRunLoop) run] + 76
17  libxpc.dylib                  	0x0000000114e208c9 _xpc_objc_main + 460
18  libxpc.dylib                  	0x0000000114e22d73 xpc_main + 143
19  com.apple.WebKit.WebContent   	0x000000010db75c0e main + 894
20  libdyld.dylib                 	0x0000000114a68955 start + 1