[ios] Use a single crash key to store breadcrumbs data.

Breakpad has a 255-byte limit on the size of a single value, but will
internally split values up to 10 ways to stay under that limit.
Breadcrumbs has similar, redundant functionality, so this CL disables it
by increasing the maximum allowed value size.

BUG=1068802

Change-Id: Ibb668f7270d6f48fb62844de88789f528b323bcd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2139996Reviewed-by: Eugene But <eugenebut@chromium.org>
Commit-Queue: Rohit Rao <rohitrao@chromium.org>
Cr-Commit-Position: refs/heads/master@{#757500}

ios/chrome/browser/crash_report/crash_report_helper.mm

@@ -41,7 +41,7 @@
 namespace breakpad {
 // IMPORTANT: be careful if ever increasing this value, Breakpad reports have an
 // overall size limit
-const int kBreadcrumbsKeyCount = 6;
+const int kBreadcrumbsKeyCount = 1;
 }
 
 // WebStateListObserver that allows loaded urls to be sent to the crash server.

ios/chrome/browser/crash_report/crash_reporter_breadcrumb_observer.h

@@ -27,6 +27,9 @@ extern const int kMaxProductDataLength;
 // Number of product data keys to use for breadcrumbs.
 @property(nonatomic) NSUInteger breadcrumbsKeyCount;
 
+// Maximum allowed length for a single product data value.
+@property(nonatomic) NSUInteger maxProductDataLength;
+
 // Starts collecting breadcrumb events logged to |breadcrumbManager|.
 - (void)observeBreadcrumbManager:(BreadcrumbManager*)breadcrumbManager;
 

ios/chrome/browser/crash_report/crash_reporter_breadcrumb_observer.mm

@@ -12,8 +12,6 @@
 #error "This file requires ARC support."
 #endif
 
-const int kMaxProductDataLength = 255;
-
 @interface CrashReporterBreadcrumbObserver () {
   // Map associating the observed BreadcrumbManager with the corresponding
   // observer bridge instances.
@@ -44,6 +42,7 @@ const int kMaxProductDataLength = 255;
 - (instancetype)init {
   if ((self = [super init])) {
     _breadcrumbs = [[NSMutableString alloc] init];
+    _maxProductDataLength = 1530U;  // 6 keys * 255 bytes/key
   }
   return self;
 }
@@ -82,7 +81,7 @@ const int kMaxProductDataLength = 255;
   [_breadcrumbs insertString:eventWithSeperator atIndex:0];
 
   NSUInteger maxBreadcrumbsLength =
-      self.breadcrumbsKeyCount * kMaxProductDataLength;
+      self.breadcrumbsKeyCount * self.maxProductDataLength;
   if (_breadcrumbs.length > maxBreadcrumbsLength) {
     NSRange trimRange = NSMakeRange(maxBreadcrumbsLength,
                                     _breadcrumbs.length - maxBreadcrumbsLength);
@@ -93,11 +92,11 @@ const int kMaxProductDataLength = 255;
   NSMutableArray* breadcrumbs =
       [[NSMutableArray alloc] initWithCapacity:self.breadcrumbsKeyCount];
   for (NSUInteger i = 0; i < self.breadcrumbsKeyCount &&
-                         (i * kMaxProductDataLength) < _breadcrumbs.length;
+                         (i * self.maxProductDataLength) < _breadcrumbs.length;
        i++) {
-    NSUInteger location = i * kMaxProductDataLength;
-    NSRange range = NSMakeRange(
-        location, MIN(kMaxProductDataLength, _breadcrumbs.length - location));
+    NSUInteger location = i * self.maxProductDataLength;
+    NSRange range = NSMakeRange(location, MIN(self.maxProductDataLength,
+                                              _breadcrumbs.length - location));
     [breadcrumbs addObject:[_breadcrumbs substringWithRange:range]];
   }
   breakpad_helper::SetBreadcrumbEvents(breadcrumbs);

ios/chrome/browser/crash_report/crash_reporter_breadcrumb_observer_unittest.mm

@@ -137,14 +137,17 @@ TEST_F(CrashReporterBreadcrumbObserverTest, MultipleKeysAttachedToCrashReport) {
           chrome_browser_state_.get());
   CrashReporterBreadcrumbObserver* crash_reporter_breadcrumb_observer =
       [[CrashReporterBreadcrumbObserver alloc] init];
-  crash_reporter_breadcrumb_observer.breadcrumbsKeyCount =
-      breakpad::kBreadcrumbsKeyCount;
+  crash_reporter_breadcrumb_observer.breadcrumbsKeyCount = 2;
+
+  const int max_product_data_length = 255;
+  crash_reporter_breadcrumb_observer.maxProductDataLength =
+      max_product_data_length;
   [crash_reporter_breadcrumb_observer
       observeBreadcrumbManagerService:breadcrumb_service];
 
   int time_size = strlen("00:00 ");
   int linebreak_size = strlen("\n");
-  int breadcrumb_size = kMaxProductDataLength - time_size - linebreak_size;
+  int breadcrumb_size = max_product_data_length - time_size - linebreak_size;
   std::string value1 = base::StringPrintf("%0*d", breadcrumb_size, 1);
   id validation_block1 = [OCMArg checkWithBlock:^(id value) {
     EXPECT_NSEQ(
@@ -186,12 +189,16 @@ TEST_F(CrashReporterBreadcrumbObserverTest, ProductDataOverflow) {
       [[CrashReporterBreadcrumbObserver alloc] init];
   // Testing with 2 keys requires less code and complexity.
   crash_reporter_breadcrumb_observer.breadcrumbsKeyCount = 2;
+
+  const int max_product_data_length = 255;
+  crash_reporter_breadcrumb_observer.maxProductDataLength =
+      max_product_data_length;
   [crash_reporter_breadcrumb_observer
       observeBreadcrumbManagerService:breadcrumb_service];
 
   int time_size = strlen("00:00 ");
   int linebreak_size = strlen("\n");
-  int breadcrumb_size = kMaxProductDataLength - time_size - linebreak_size;
+  int breadcrumb_size = max_product_data_length - time_size - linebreak_size;
   std::string value1 = base::StringPrintf("%0*d", breadcrumb_size, 1);
   id validation_block1 = [OCMArg checkWithBlock:^(id value) {
     EXPECT_NSEQ(